Method and device for generating control data for an additive manufacturing device

ABSTRACT

Described are a method and a control data generation device (54, 54′) for use therein for generating control data (PSD) for a device (1) for the additive manufacture of a manufacturing product (2) in a manufacturing process, in which build-up material (13) is built up and selectively solidified, wherein, for the solidification process, the build-up material (13) is irradiated with at least one energy beam (AL) on a build field (8), and an area of incidence (AF) of the energy beam (AL) on the build field (8) is moved in order to melt the build-up material (13). The control data (PSD) are generated such that the energy beam (AL) has an intensity distribution (GIV), at the area of incidence (AF) on the build field (8), in a section plane (x, y) running perpendicularly to the beam axis (SA) of the energy beam (AL), which intensity distributionhas at least one local minimum (MIZ) in a middle region along at least one secant of the intensity distribution (GIV) in the section plane (x, y) andhas an intensity profile curve (IPK), running along the edge (R) of the intensity distribution (GIV), which intensity profile curve has, at least at one point, a maximum value (MAX), and, at least at one point in a region opposite the maximum value (MAX) on the intensity profile curve (IPK), a minimum value (MIN).Also described are a method and a control device (50) for controlling a device (1) for the additive manufacture of a manufacturing product (2) using this control data (PSD), and a device (1) for the additive manufacture of manufacturing products.

The invention relates to a method and a control data generation devicefor generating control data for a device for the additive manufacture ofa manufacturing product in a manufacturing process in which build-upmaterial is built up and selectively solidified. Here, for thesolidification process, the usually shapeless or flowable, generallypowdery, build-up material is irradiated with at least one energy beamon a build field, and an area of incidence of the energy beam on thebuild field is moved in order to melt the build-up material, at leastlocally in the region of the area of incidence or in a target region inand around the area of incidence. Furthermore, the invention relates toa method and a control device for controlling a device for the additivemanufacture of a manufacturing product using said control data, and to adevice for the additive manufacture of manufacturing products.

Methods for irradiating a material with an energy beam, for example alaser beam or the like, in particular for local melting of the material,are required in many processes. A typical example of this is weldingwith an energy beam, or rather laser welding. Another large area ofapplication is in additive manufacturing. Additive manufacturingprocesses have become increasingly relevant in the production ofprototypes and individual manufacturing products, and in the meantimealso in series production. In general, “additive manufacturingprocesses” are understood to be those manufacturing processes in which amanufacturing product (hereinafter also referred to as a “component”) isbuilt up generally on the basis of digital 3D construction data bydepositing material (the “build-up material”). The build-up is usually,but not necessarily, performed layer by layer. The term “3D printing” isoften used as a synonym for additive manufacturing; the production ofmodels, samples and prototypes by additive manufacturing processes isoften referred to as “rapid prototyping”; and the production of tools as“rapid tooling”. A key point in these processes is the selectivesolidification of a build-up material, and this solidification can beachieved in many manufacturing processes with the aid of irradiationwith radiant energy, for example electromagnetic radiation, inparticular light and/or heat radiation, but optionally also withparticle radiation, such as electron radiation. Examples of methods thatutilise irradiation are “selective laser sintering” or “selective lasermelting”. In this process, thin layers of a usually powdery build-upmaterial are repeatedly applied one on top of the other, and in eachlayer the build-up material is selectively solidified by spatiallydelimited irradiation of the areas that, after manufacture, are to bepart of the manufacturing product that is to be produced, in that thepowder grains of the build-up material are partially or completelymelted with the help of the energy locally introduced by the radiationat this location. After cooling, these powder grains are then bondedtogether in a solid.

The selective irradiation, in particular the movement of an area ofincidence of an energy beam on the build field, is, preferably alsowithin the scope of the present invention, usually carried out inaccordance with a suitable irradiation strategy. In this regard, themovement may be a deflection of the previously generated energy beam orenergy beam bundle as is provided with the usual “scanning”, for exampleby galvanometer mirrors in the case of a laser beam, or byelectromagnetic deflection in the case of an electron beam or ion beam.If necessary, a movement can also (at least partially) be effected by amovement of the beam delivery unit or irradiation device, in particularan energy beam source, itself, for example in the form of a movablediode bank, in particular a laser diode bank.

As a rule, larger two-dimensional regions, i.e. larger areas on thebuild field, are to be irradiated during a solidification process.Irrespective of how the energy beam is generated and how exactly thepoint of incidence on the build field is moved, it has provenadvantageous to first virtually “divide” the regions to be irradiatedaccording to a selected pattern, for example into virtual “stripes”, adiamond pattern, a chequerboard pattern or the like. The individualareas of this pattern, for example the stripes or fields, are thenusually run over with the energy beam in the form of a so-called“hatching” (also referred to generally and hereinafter as a “hatch”). Ina striped pattern, for example,—viewed macroscopically—the build-upmaterial is thus gradually solidified along parallel strips, and indetail—viewed microscopically—the area of incidence of the energy beamon the build field moves along hatching lines which are arranged closelynext to one another and run transversely to the respective irradiationstrips in the boundaries of the irradiation strip.

In practical applications or in the machines or devices known hithertofor additive manufacturing, energy beams are usually used, for examplelaser beams, which have substantially rotationally symmetrical (i.e.circularly symmetrical) intensity distributions. Such a rotationallysymmetrical intensity distribution often corresponds to a Gaussianprofile. In a Gaussian intensity distribution, the intensity is highestin the centre of the energy beam and weakens in all directions radiallyoutwards transversely to the direction of propagation or the currentbeam path direction of the energy beam (hereinafter also referred to as“beam direction” or “beam axis” for short) according to a Gaussianfunction or Gaussian curve. This intensity distribution can be obtainedwithout further measures from the energy beam sources used hitherto, forexample a common laser.

However, the latest findings or research show that the exact shape ofthe intensity distribution of the energy beam, in particular the laserbeam, can certainly have a not inconsiderable influence on the entiremanufacturing process, in particular, for example, on the efficiency andthus also on the specific energy consumption and/or the quality of themanufacturing product, for example its microstructure. A comparisonbetween a laser beam with a Gaussian intensity distribution and anon-rotationally symmetrical intensity distribution, namely anelliptical intensity distribution, is described, for example, in Tien T.Rohling et al., “Modulating laser intensity profile ellipticity formicrostructural control during metal additive manufacturing” in ActaMaterialia, 128 (2017), pp. 197-206. Here, it is also shown that notonly the intensity distribution itself, but also its orientation inrelation to the current direction of movement of the energy beam or itsarea of incidence on the build field (hereinafter also referred to asthe “scanning direction” without limitation of generality) can have animpact on the manufacturing process.

For example, in practice, laser sintering or laser melting of metals iscurrently mostly carried out with a so-called “deep welding process”(“keyhole mode welding”). A welding process is defined as a deep weldingprocess when a vapour capillary, also called a “keyhole”, forms. Theincident energy beam, especially a laser beam, in this case creates aweld pool of molten material or metal. If the weld pool surface of thematerial reaches its boiling temperature due to continued irradiation,the vapour bubble pushes the melt away laterally and downwards, thuscreating the vapour capillary. The diameter of this keyhole is oftensmaller than that of the energy beam or laser beam. One advantage ofthis deep welding process is the high depth effect. This means that adeeper weld pool is formed in relation to the beam diameter than wouldbe the case if such vaporisation did not take place. A welding processor melting process without vaporisation is referred to hereinafter as“heat conduction welding” (also “conduction mode welding” or “conductionlaser welding”).

However, such a deep welding process also has a number of disadvantages:

On the one hand, a relatively high energy has to be provided by theenergy beam in order to vaporise the material. The enthalpy ofvaporisation of the material is usually about two to five times higherthan the enthalpy of fusion and is removed from the productive part ofthe process. Although the enthalpy of vaporisation is released againduring the condensation of the metal vapour, it can no longer be usedproductively for the process. This energy consumption increases thecosts of the process.

Secondly, in order to maintain process stability, the vaporised materialis usually largely removed from the process zone and in some cases evenfiltered out of the process atmosphere and disposed of. Given the highcost of metal powder, this can make component prices noticeably moreexpensive.

Thirdly, during vaporisation, the volume of the material (under normalconditions) increases by a factor of about 1000. This leads to highpressures in the metal vapour within the vapour capillary, or keyhole,which in turn can result in very high outflow speeds (of the order ofMach 0.3) of the metal vapour from the keyhole. This gas jet entrainsneighbouring solid particles and/or droplets leaving the weld pool,causing further material losses. These particles and/or droplets areusually referred to as “spatter”.

Fourthly, the metal gas usually flows exactly against the direction ofincidence of the energy beam and condenses in the process. The incidentenergy beam can interact uncontrollably with this outflowing andcondensing metal gas by absorption and scattering. To largely avoid thisprocess-relevant disturbance, the flow direction of the metal gas can bediverted as quickly and efficiently as possible. This can be done, forexample, with a flow curtain of shielding gas oriented tangentially tothe powder bed, the speed of which gas curtain must, however, be highenough to sufficiently reduce the undesirable effects. However, the flowspeed is then generally so high that relevant quantities of powderymaterial can also be entrained from the powder bed, just as strong windentrains dust from the ground (wind erosion). By means of a process gasrecirculation system, process by-products or impurities, such as metalcondensate or raw powder, are generally removed from the process chamberand can be collected downstream of the process chamber in filters and,optionally, separators of the exhaust air system. This material is oftenlost and must also be disposed of in a time-consuming and cost-intensivemanner.

The material losses from the various loss sources explained above canamount to a not inconsiderable proportion of the weight of the assembledcomponents. Therefore, their avoidance or significant reduction wouldhave a noticeable cost-reducing effect.

Which welding process is more suitable in a specific case can depend onvarious constraints and can also change during the manufacturingprocess, for example depending on the location within the component tobe manufactured. Whether the welding process is carried out as a heatconduction welding process or as a deep welding process again depends onvarious parameters. An essential parameter can also be the shape of theintensity distribution.

It is an object of the present invention to disclose a suitable methodand a corresponding control data generation device for generatingcontrol data, as well as a method for controlling a device for theadditive manufacture of a manufacturing product and a control devicesuitable herefor, as well as a device for additive manufacturing, inwhich an energy beam is used which is particularly well suited for aheat conduction welding process.

This is solved, on the one hand, by a method for generating control data(hereinafter also referred to as a “control data generation method”)according to claim 1 and by a control data generation device accordingto claim 12 and, on the other hand, by a method for controlling a devicefor the additive manufacture of manufacturing products (hereinafter alsoreferred to as the “control method”) according to claim 11, a controldevice for an additive manufacturing device according to claim 13, andan additive manufacturing device according to claim 14.

In a method according to the invention, the control data for a devicefor the additive manufacture of a manufacturing product in amanufacturing process explained above are generated such that the energybeam has an intensity distribution, at the area of incidence on thebuild field, in a section plane running perpendicularly to the beam axis(i.e. perpendicularly to the beam direction or direction of incidence)of the energy beam, which intensity distribution has the featuresdefined below.

In this regard, it should first be noted that, in general, an “intensitydistribution” of an energy beam within the meaning of the presentapplication comprises the spatial shape or extent of the energy beam ina section plane (cross-sectional area) perpendicularly to the beamdirection or beam axis and also the spatial distribution of theintensity over the cross-sectional area, i.e. in particular thepositions of maxima and minima, etc. The wording “at the area ofincidence on the build field” is to be understood as referring to theintensity distribution in the section plane perpendicularly to thedirection of incidence shortly before the area of incidence, which inmost situations does not correspond to the intensity distributiondirectly on the surface of the build field or in the working plane,since the energy beam usually strikes the build field at an angle.However, this does not exclude the possibility that, during the courseof the process, said section plane will always coincide with the area ofincidence, since the energy beam is at that moment perpendicular to thearea of incidence.

According to the invention, this intensity distribution of the energybeam generated on the basis of the control data is parameterised asfollows:

On the one hand, the intensity distribution according to the inventionhas, in a middle region, at least one local minimum along at least onesecant (an edge curve) of the intensity distribution in the sectionplane extending perpendicularly to the beam axis of the energy beam. A“secant” in the sense of the present invention runs from one side to theother side through an area of the intensity distribution, i.e. itintersects the edge of the intensity distribution at exactly two pointsspaced apart from each other, irrespective of the exact shape or courseof the edge curve or edge, and may, but need not, run through the beamaxis or the centre of the intensity distribution (in this case thesecant would correspond to a diameter). In particular, the secant doesnot lie exclusively on the edge curve. Preferably, the secant runstransversely, preferably substantially perpendicularly, to the scanningdirection of the energy beam on the build field. Also preferably, thesecant runs through a geometric centre of gravity of the shape or formof the intensity distribution in the section plane.

The “middle region” is understood here to be a central region of theintensity distribution, i.e. the local minimum is located in the regionof the secant that runs through this middle region. It is distinguishedfrom an edge region of the intensity distribution, which runs along anedge of the intensity distribution and extends from the edge into theintensity distribution, more specifically preferably to such an extentthat an area share of the edge region in the total area content of theintensity distribution comprises at least 10%, preferably at least 20%and/or at most 50%, preferably at most 40%. With reference to the caseof a circular intensity distribution, the edge region accordinglyextends, for example, by 10% or by 20% of the radius of the intensitydistribution from the edge into the intensity distribution. Here, the“edge” of the intensity distribution is arbitrarily defined such that99% of the radiant power of the energy beam is located within the edge(i.e. in the area enclosed by the edge).

On the other hand, the intensity distribution according to the inventionpreferably has a (completely) circumferential intensity profile curvewhich is shifted inwards along the edge of the intensity distribution,substantially parallel to the edge, and which has a maximum value atleast at one point and a local minimum value in a region opposite themaximum value on this intensity profile curve. An “intensity profilecurve” is understood here to be an intensity profile of the intensitydistribution as a function of location along a defined, appropriatelyselected curve. The term “local minimum value” is to be understood herein such a way that it is a minimum value with regard to the course ofthe intensity values on this intensity profile curve, i.e. if theintensity is measured along this intensity profile curve and plotted ina diagram, a local minimum value is shown here.

A “region opposite” the maximum value on the intensity profile curvemeans a region which in both directions along the intensity profilecurve encloses at most an angle of 60°, preferably at most 50°, furtherpreferably at most 40°, further preferably at most 30°, particularlypreferably at most 10° starting from the position (diametrically)opposite the maximum value on the intensity profile curve. Veryparticularly preferably, the local minimum value is substantially (i.e.within the usual tolerances) diametrically opposite the maximum value onthe intensity profile curve. In a narrower sense, the term“diametrically” refers in particular to circular intensity profilecurves. More generally, however, i.e. also in the case of an irregularshape of the intensity profile curve, a corresponding opposite pointcan, for example, be constructed in such a way that, starting from themaximum value, a secant is laid through the centre of gravity of thearea enclosed by the edge of the intensity distribution; where thesecant intersects the intensity profile curve again is then the“diametrically” opposite point within the meaning of this application.

With this preferred intensity distribution, it is thus ensured that ahigher intensity is deliberately achieved in a peripheral region alongthe edge, at least in some sections, preferably all around, than in acentral region. A local minimum is located in the centre, i.e. at thebeam axis and/or at a short distance from it, for example within half adistance from the centre to the edge.

The second parameterisation of the intensity distribution with a maximumvalue and an opposite minimum value on an intensity profile curverunning along the edge also ensures that the intensity distribution isdeliberately not rotationally symmetrical with respect to a rotationaxis running coaxially to the direction of incidence of the combinationenergy beam on the material or build field.

The term “rotationally symmetrical” here refers to a rotation axis thatis coaxial to a beam direction of the energy beam. Until now, as alsomentioned above, the energy beams are usually generated in such a waythat they are rotationally symmetrical, namely, for example, have theaforementioned Gaussian intensity distribution. In contrast, in thefollowing, the term “non-rotationally symmetrical” or “substantiallynon-rotationally symmetrical” is to be understood as those energy beamswhose intensity distribution has been deliberately generatednon-rotationally symmetrically to a significant degree and/or has beeninfluenced accordingly by the targeted modification of a beam and/or bythe superimposition of energy beams to obtain a combination energy beamwith a non-rotationally symmetrical overall intensity distribution. Thisdoes not include energy beams that should, per se, have a usualrotationally symmetrical, for example Gaussian, intensity distributionand merely exhibit undesirable deviations from rotational symmetry, forexample due to unintentional distortions or other imperfections of thesystem for generating and/or moving the energy beam. For example, if theintensity distribution of the output energy beam generated in thedesired manner were to be mathematically defined as a function I(r, ϕ)of the location in polar coordinates r and ϕ (in a plane perpendicularto the beam direction), then the intensity distribution could preferablybe described or defined as “non-rotationally symmetrical” if no point oforigin can be found within the intensity distribution which, for any m,under the condition m≥2 and any r, satisfies the following property:

${{1 - \left( \frac{I\left( {r,\phi_{0}} \right)}{I\left( {r,{\phi_{0} + {360{^\circ}\text{/}m}}} \right)} \right)}} < ɛ$

wherein ε≤0.01, preferably ε≤0.05, further preferably ε≤0.1 even furtherpreferably ε≤0.2. More precisely, an intensity distribution defined inthis way is not rotationally symmetrical in any dimension.

An intensity distribution parameterised in the manner according to theinvention allows a simpler setting of a target temperature on the buildfield in the region of the area of incidence in order to keep themelting process within the process window of heat conduction welding. Aswill be explained in more detail later on the basis of a specificembodiment example using virtual functional regions, a relatively fastheating of the material can be achieved with the region around themaximum value. The higher intensity present in a peripheral region alongthe edge, at least in some sections, than in a central region serves tocompensate for the heat losses from the active process zone, i.e. fromthe area of incidence, into the surrounding build-up material. Themiddle region of the intensity distribution surrounded by these regionsserves to adjust and control the temperature profile in the melt so thatthe desired process range of heat conduction welding can be maintained.

In a method according to the invention for controlling a device for theadditive manufacture of a manufacturing product, control data are firstgenerated in the manner according to the invention and are then used tocontrol the device with the control data. In this case, the control datacan be generated in advance and transmitted as a complete data packageor as a type of “control protocol” to the device, which then carries outthe production process. In principle, however, it would also be possibleto determine control data during the already running process forsubsequent process steps, for example while a layer is being solidified,to determine the control data for the next layer and to use it duringthe solidification of the further layer. This means that the controldata can also be modified dynamically during the process, for examplealso on the basis of process monitoring data or quality data based onthis.

The starting point for the control data is, among other things, datathat indicate at which points within the process area or theconstruction area material is to be solidified, i.e. which parts arelater to belong to the component or to any support structures or thelike and which regions are not. This data can be taken, for example,from a digital 3D model of the object to be manufactured and/or thesupport structures. If these data and further required information areavailable, such as which material is used, which solidification device,in particular which type of energy beam, is available or within theframework of which parameters this is adjustable, etc., an intensitydistribution that is optimised or optimal for the case in question andthat fulfils the above-mentioned features according to the invention canthen be determined, and the control data can be generated accordingly.

The control data according to the invention can basically be exposurecontrol data or scan data. Among other things, these can also define orprescribe the movement of the energy beam over the surface, as well asthe level of the energy or laser intensity and/or an extent of the beamperpendicularly to the beam direction. In particular, however, thecontrol data comprise data or information for an irradiation device ofthe additive manufacturing device regarding the above-defined desiredintensity distribution or the intensity distribution to be set or“shape” of the beam perpendicularly to the beam direction at the area ofincidence. In addition, the control data as a whole can also includeother data required for other components of the additive manufacturingdevice of a manufacturing product, such as information about the layerthickness, etc.

A control data generation device according to the invention forgenerating control data for a device for the additive manufacture of amanufacturing product is correspondingly designed in such a way that thecontrol data are generated in such a way that the energy beam has anintensity distribution, at the area of incidence on the build field, ina section plane running perpendicularly to the beam axis of the energybeam, which intensity distribution

-   -   has at least one local minimum in a middle region along at least        one secant of the intensity distribution in the section plane        and    -   has an intensity profile curve, running along the edge of the        intensity distribution, which has, at least at one point, a        maximum value, and, at least at one point in a region opposite        the maximum value on the intensity profile curve, a minimum        value.

The control data generation device can, for example, be part of acontrol device of such a manufacturing device for the additivemanufacture of a manufacturing product. However, it can also beimplemented independently on another computer in order to then transferthe data to the control device.

Accordingly, a control device according to the invention for such adevice for the additive manufacture of a manufacturing process has acontrol data generation device according to the invention or aninterface to such a control data generation device for providing therelevant control data or for transferring the control data from thecontrol data generation device, and this control device is designed tocontrol the additive manufacturing device for irradiating the build-upmaterial with the energy beam using this control data. The controldevice preferably ensures coordinated control of all components of theadditive manufacturing device. In particular, the control device canalso comprise a plurality of sub-control devices which are assigned, forexample, to the irradiation device, in particular to the first and/orsecond energy beam movement unit mentioned later, and/or to othercomponents and which cooperate in a suitable manner. The control deviceor the sub-control devices can—as explained later—also be implementedcompletely or partially in the form of software.

A device according to the invention (hereinafter also referred to as a“manufacturing device”) for the additive manufacture of manufacturingproducts in an additive manufacturing process has, in addition to theusual components, such as a feed device (often also referred to as a“coater”) for introducing build-up material—for example in the form of alayer of build-up material, which in particular, as mentioned, isshapeless or flowable—into a process area, and an irradiation device forselectively solidifying the build-up material by irradiation of at leastone such control device by means of an energy beam.

It should be noted at this juncture that the device according to theinvention can also have a plurality of irradiation devices, which arethen controlled in a correspondingly coordinated manner with the controldata. It should also already be mentioned that, in this respect, theenergy beam, the intensity distribution of which is to have the featuresaccording to the invention, can also consist of a plurality ofsuperimposed energy beams, as will be explained later. Accordingly, thecontrol signals for the individual components for generating the energybeams would then have to be generated so that the desired result withregard to the intensity distribution is achieved overall. Similarly, theirradiation devices can be used to generate a plurality of separateenergy beams with the features according to the invention in order toconsolidate material in parallel at a number of positions on the buildfield. A combination of these variants is also possible.

The control data generation device according to the invention can—justlike other parts of the control device or the control device as awhole—be realised in the form of a computer unit with suitable software.The computer unit may, for example, have one or more cooperatingmicroprocessors or the like for this purpose. In particular, the controldata generation device may be implemented in the form of suitablesoftware program parts in the computer unit of a control device of amanufacturing device according to the invention. A largelysoftware-based realisation has the advantage that computer units alreadyin use, in particular control devices of manufacturing devices foradditive manufacturing, can be retrofitted in a simple manner by meansof a software or firmware update in order to operate in the manneraccording to the invention.

In this respect, the object is also achieved by a corresponding computerprogram product with a computer program which can be loaded directlyinto a memory device of a computer unit, in particular a control device,with program sections to execute all steps of the method according tothe invention when the program is executed in the computer unit orcontrol device. In addition to the computer program, such a computerprogram product may optionally comprise additional parts, such asdocumentation and/or additional components, including hardwarecomponents, such as hardware keys (dongles, etc.) for using thesoftware. A computer-readable medium, for example a memory stick, a harddisk or another transportable or permanently installed data carrier, onwhich the program sections of the computer program that can be read andexecuted by a computer unit, in particular the control device, arestored, can be used for transport to the computer unit or control deviceand/or for storage on or in the computer unit or control device.

Further, particularly advantageous embodiments and further developmentsof the invention will become clear from the dependent claims as well asthe following description, wherein the independent claims of one claimcategory can also be further developed analogously to the dependentclaims and embodiment examples of another claim category and, inparticular, individual features of different embodiment examples orvariants can also be combined to form new embodiment examples orvariants.

As will be explained later with reference to embodiment examples, it maybe particularly preferred to ensure that the intensity distribution hasa local intensity increase extending in an at least partially annularcircumferential edge region (or in a segment of the annular edge region)of the intensity distribution. In other words, in at least one regionalong its contour at a short distance from the edge, the intensitydistribution has an increased intensity in relation to a middle region(i.e. a local maximum region in relation to a surrounding environment).Here, the edge region is again to be understood as the region betweenthe central region defined above and the edge. The circumferentialintensity profile curve preferably runs along the partially ring-shapedcircumferential edge area, at least in some sections.

The local increase in intensity at one point on the intensity profilecurve and the local minimum in the region on the opposite side of theintensity profile curve can, in particular, produce an intensitydistribution with a kind of crescent-shaped increase in intensity.

Preferably, it is ensured that the maximum value on the circumferentialintensity profile curve lies in an edge region of the intensitydistribution lying at the front in a scanning direction.Correspondingly, the local minimum on the intensity profile curve wouldlie in an edge region lying at the rear in the scanning direction. Thisdoes not exclude the existence of further local maxima and local minimaon the intensity profile curve.

The “forward edge region” in the scanning direction may preferably be adistance over a radian measure of at most approximately ⅔π·r (r is herethe radius of orbit, which, depending on the beam shape, may beequivalent to the radius of curvature. It can be defined here for anybeam shape or shape of the intensity distribution that the circumferenceof the profile of the beam shape is defined as 2·π·r), furtherpreferably of at most approximately ½π·r, even further preferably of atmost approximately ⅓π·r, particularly preferably of at mostapproximately ⅙π·r, wherein the area covered by the resulting angularrange includes the point of the intensity distribution located at thefront in the scanning direction.

In particular, a circular intensity distribution can thus be an angularrange (in the case of a circular intensity distribution around a ringsegment) of at most approximately 120°, further preferably of at mostapproximately 90°, even further preferably of at most approximately 60°,particularly preferably of at most approximately 30°, wherein the areacovered by the angular range includes the point of the intensitydistribution located at the front in the scanning direction.

Preferably, the minimum value on the intensity profile curve is higherthan the local minimum in the middle region, i.e. in the centre or nearthe centre of the intensity distribution.

In the region of the minimum in the middle region, the intensity ispreferably a maximum of 1.5 MW/cm². Preferably, the intensity here is atleast 0.05 MW/cm².

Preferably, the intensity on the intensity profile curve running alongthe edge is, at any point, higher than the local minimum in the middleregion of the intensity distribution. In other words, the intensitydistribution has a complete annular intensity increase in the edgeregion, but the magnitude of the intensity increase varies depending onthe location over the circumference.

The ratio of the intensity of the maximum value on the circumferentialintensity profile curve, for example in a point of the local intensityincrease running along the edge, to the intensity in a local minimum, inparticular in the middle region of the intensity distribution, ispreferably a maximum of 10:1, preferably a maximum of 9:1, furtherpreferably a maximum of 8:1, particularly preferably 7:1.

Preferably, the ratio of the intensity of the minimum value on thecircumferential intensity profile curve to the intensity in a localminimum is at least 1.5:1, preferably at least 2:1, further preferablyat least 3:1, particularly preferably at least 4:1.

Preferably, the maximum value on the intensity profile curve runningalong the edge is at least one and a half times, further preferably atleast twice, even more preferably at least three times, particularlypreferably at least four times higher than the local minimum value inthe region opposite on the intensity profile curve. The maximum value onthe intensity profile curve running along the edge is also preferably atmost eight times, further preferably at most seven times, even furtherpreferably at most six times, particularly preferably at most five timeshigher than the local minimum value in the region opposite on theintensity profile curve.

Between the maximum value and the minimum value in the region oppositeon the intensity profile curve, the (location-dependent) function of theintensity values along the intensity profile curve can in principle runas desired. It is particularly preferably curved. It is preferably a“smooth” function without jumps. Preferably, this function isdifferentiable at least once at each point, preferably is differentiableat least twice, particularly preferably is differentiable any number oftimes.

However, this does not exclude that the intensity distribution can inprinciple also be defined by a step function or a number of superimposedstep functions.

Preferably, the intensity distribution of the energy beam can be set tobe substantially axially symmetrical or substantially non-axiallysymmetrical, depending on an area of incidence environment parameter,with respect to an axis of symmetry lying in the scanning direction.

An “axially symmetrical” setting means that an axial symmetry existswithin the usual tolerances. A “substantially non-axially symmetrical”setting means that this axis symmetry is deliberately not observed, i.e.there is a deviation from the axis symmetry beyond the usual tolerances.

The area of incidence environment parameter can in particular beunderstood as a parameter indicating whether the current track (forexample a hatch) runs next to already solidified material, i.e. whetherfor example a first track is drawn that is not laterally adjacent to aprevious track, or whether it is a further track.

Since solidified material has different thermophysical properties thanunsolidified material, compensation can be achieved by deliberatelydeviating from the axis symmetry. For this purpose, it can be ensured,for example, that the maximum value on the intensity profile curverunning along the edge is not exactly at the front in the scanningdirection, but a little further away from or closer to the alreadysolidified track (for example the already processed neighbouring hatch).In other words, the entire intensity profile curve is rotated away fromor towards the already solidified track with respect to the maximumabout the rotation axis of the intensity profile curve. At the sametime, it is ensured that the minimum value on the intensity profilecurve of the intensity distribution is rotated towards or away from thealready solidified track. The direction in which the rotation takesplace can depend, for example, on whether the immediately adjacent,already solidified track is still hot or has already cooled down. Acooled, hardened track has more mass and absorbs energy more poorlybecause a “smooth” surface reflects more radiation. When a track iscooled down, the maximum of the neighbouring track to be subsequentlysolidified will therefore preferably be closer to this previouslysolidified track than when it is still hot and already contains moreenergy, so that less new energy has to be introduced.

There are various ways to generate an energy beam with the desiredintensity distribution.

For example, the desired beam shaping could take place already when theenergy beam is generated. For example, a laser could be constructed withmany laser channels that can be coherently combined to act and functiontogether as a single coherent laser source. This could inherently offerthe possibility to additionally modulate each individual laser channelhighly dynamically in phase and amplitude to achieve the desiredvariable beam shaping, in particular the desired intensity profile.

Furthermore, an energy beam generated by an energy beam source, i.e.also initially rotationally symmetrical, can only be “shaped” ormodified afterwards within a beam shaping device in order to obtain thedesired intensity distribution. Such a beam shaping device can also berealised in various ways.

Preferably, the beam shaping device can have at least one micro-opticalelement that can be controlled by a control device. A so-calleddiffractive optical element (DOE) is particularly preferred. DOEs canwork reflectively or transmissively, for example, and change thewavefront of an incident beam by locally modulating the phase and/oramplitude of the reflected or transmitted partial beams.

Since—sometimes very fast—changes of direction can also occur duringirradiation and, as a rule, a certain intensity distribution is alwaysdefined in relation to the current direction of movement, i.e. scanningdirection, the direction of the ideal intensity distribution on thebuild field or material must change frequently (for example, in order toalign the maximum value with the current hatch direction, as mentionedabove). This requires a fast response of the irradiation device withrespect to changes in the intensity distribution. Another point is that,depending on the exact manufacturing parameters, relatively high spatialintensity differences within the intensity distribution are desirable,as have already been partly defined above.

In order to provide an energy beam of which the intensity distributioncan have high spatial intensity differences and which can neverthelessbe changed quickly, a method can be used, for example, in which controldata are generated for the generation of at least two energy beams—andaccordingly also two energy beams—so that the intensity distribution isgenerated by a superimposition of the energy beams.

In other words, at least a first energy beam and a second energy beamare generated. This can be done, for example, by an energy beam sourcesystem with at least two separate energy beam sources, for example twolasers. In principle, however, it would also be possible for the energybeams to be generated first by one energy beam source and then to besplit, for example in a beam splitter or the like.

Preferably, the control data are generated in such a way that a firstenergy beam together with a second energy beam at least partiallysuperimposed as a “combination energy beam” is moved over the materialor build field in a coordinated manner at a predetermined scanningspeed, which can also be changed dynamically.

Particularly preferably, a, preferably cyclic and/or preferablycontinuous, relative movement of the second energy beam with respect tothe first energy beam takes place simultaneously with a predeterminedrelative speed (which can also be dynamically controlled), the magnitudeof which is much greater than the magnitude of the scanning speed.

This combination energy beam can then, as will be explained in moredetail, have a (time-integrated) “overall intensity distribution” whichhas the features of the invention as defined above.

Preferably, the magnitude of the relative speed between the first energybeam and the second energy beam or of the first energy beam within thecombination energy beam is at least twice as great as the magnitude ofthe scanning speed, further preferably at least five times greater, evenfurther preferably at least ten times greater, particularly preferablyfifty times greater and very particularly preferably even one hundredtimes greater.

Therefore, the amount of the relative speed can preferably be at least 5m/s. It is particularly preferably at least 10 m/s, further preferablyat least 20 m/s and very particularly preferably at least 50 m/s.

The magnitude of the scanning speed, on the other hand, is usually in arange of 0.01 m/s to 5 m/s, for example in the case of selective lasermelting or selective laser sintering. In the case of electron beammelting, on the other hand, significantly higher speeds can also beachieved, for example 20 m/s or more. This means that the scanningmovement is generally considerably slower than the relative movement ofthe second energy beam with respect to the first energy beam.

By moving the second energy beam relative to the first energy beam, ineach case time-integrated “overall intensity distributions” of thecombination energy beam can advantageously be generated over a certainperiod of time with almost any design. This integration time periodshould preferably be sufficiently long to allow the second energy beamto substantially traverse its path relative to the first energy beam.Therefore, in the case of a cyclic movement—already mentioned above andexplained in more detail later—the integration time period couldcomprise at least one cycle of movement of the second energy beamrelative to the first energy beam. Preferably, the integration timeperiod is a longer period of time, for example an integer multiple ofone movement cycle.

Since the area of incidence of the “combination energy beam” on thematerial moves, a relatively fast relative movement of the second energybeam with respect to the first energy beam can ensure that, during ascanning of the build field with the combination energy beam, asufficient “residence time” (or “irradiation time period”) is present ateach location so that at least approximately the previously mentionedintegration time period is achieved. In other words, the relative speedshould preferably be high enough that the superimposed intensitydistributions of the first and second energy beams act on the build-upmaterial as a “quasi-stationary” overall intensity distribution in thetime period of the physical process of heat conduction due to theinertia of the thermal diffusion (dissipation of heat). Consideredvisually, the material is thus basically supplied with a radiant energycorresponding to the overall intensity distribution over the integrationtime period, since, due to the lower scanning speed during the residencetime (which is long in relation to the relative movement) of thecombination energy beam at a location, the second energy beam with itsintensity distribution within the overall intensity distribution of thecombination energy beam scans all relative positions, preferably evenscans several times, if the scanning movement (for this image) were tobe considered non-existent. In a continuous scanning motion, there is ofcourse always a small local offset with each revolution, but this doesnot significantly affect the heat distribution in the vicinity of theactual area of incidence due to the typically high scanning speeds andrelatively slow thermal diffusion, and therefore the image referencedabove approximately reflects the conditions well. In other words, it isensured that the material to be melted or the material region “sees” anapproximately “stationary” overall intensity distribution of thecombination energy beam at a certain point in time when the combinationenergy beam hits the region in question. The minimum relative velocityrequired for this can therefore also depend significantly on thematerial parameters of the build-up material used, in particular thespecific heat capacity. For example, it can be ensured that the Fouriernumber Fo=(a−Δt)/d² is as small as possible in order to achieve the“quasi-stationary” overall intensity distribution as well as possible,where a is the thermal diffusivity (material constant), Δt is acharacteristic time period (for example the period duration) and d is acharacteristic length (for example an extent, such as the radius, of theoverall intensity distribution). The smaller the Fourier number, theless heat is “transported away” in the time period under consideration,i.e. the period of one revolution of the second energy beam.

The “relative movement” of the second energy beam with respect to thefirst energy beam or the position of the beam axis of the second energybeam within the overall intensity distribution of the combination energybeam can comprise a very wide range of geometric paths or path curves(courses of a scanning path), i.e. translatory or rotatory movements ormovement patterns. Particularly preferably, as mentioned, the relativemovement of the second energy beam with respect to the first energy beamand/or the position of the second intensity distribution of the secondenergy beam within the overall intensity distribution runs on a closedcurve, i.e. can be described as “periodically stationary”. For example,the second energy beam can perform a circular or elliptical movementwithin the combination energy beam, or relative to the first energybeam, or move along a closed polygonal path. Likewise—depending on thespecific requirement—as mentioned, other arbitrary curves are alsopossible, such as any other polygonal shape, a zig-zag line, asinusoidal sweep (also known as oscillatory welding), etc., as long asthe time-integrated “overall intensity distribution” of the combinationenergy beam generated by the superimposed energy beams (consideredquasi-stationary) fulfils the features of the invention as definedabove, i.e. the “overall intensity distribution” of the combinationenergy beam can have any shape or form within these limits.

Such a method for irradiating a material, in which a first energy beamand a second energy beam are generated and at least partiallysuperimposed in the manner described and moved over the material at apredetermined speed, the second energy beam being moved relative to thefirst energy beam at a predetermined relative speed, the magnitude ofwhich is much greater than the magnitude of the scanning speed, could inprinciple be achieved by a simple coordinated or synchronised control oftwo separate energy beam movement units or scanners over the buildfield.

In this case, the irradiation device according to the invention requiresan energy beam source system for generating at least a first energy beamand a second energy beam, as well as a first energy beam movement unitand a second energy beam movement unit, and a control device whichcontrols the irradiation device in such a way that the first energy beamand the second energy beam are at least partially superimposed as acombination energy beam and moved in a coordinated manner over thematerial or build field at a predetermined scanning speed, the secondenergy beam being moved relative to the first energy beam.

However, the following procedure can be used particularly preferably:

The second energy beam is moved relative to the first energy beam, andthe first energy beam and the second energy beam moving relative theretoare then already coupled into an energy beam movement unit in a commonbeam path in such a way that they are moved together as a combinationenergy beam, for example over the build field with the build-up materialin an additive manufacturing process. In this case, it is thus ensuredthat the energy beams run, for example, parallel or coaxially along thesame beam path, and the current relative position of the intensitydistributions of the first energy beam and the second energy beam in asection plane running perpendicularly to the beam axis of thecombination energy beam (i.e. the virtual beam axes—defined later—or acorresponding beam path) does not change significantly on the paththrough the relevant energy beam movement unit from the coupling pointinto the energy beam movement unit, for example when using a scanner onthe first scanner mirror, to the area of incidence. For example, if theintensity distribution of the first energy beam or the first energy beamitself is mirrored or rotated, the intensity distribution of the secondenergy beam or the second energy beam itself is simultaneously mirroredor rotated, etc.

The relative position between the first energy beam and the secondenergy beam is thus determined substantially only by the movement of thesecond energy beam relative to the first energy beam before the couplinginto the energy beam movement unit for the combination energy beam.Here, the movement of the second energy beam “relative to the firstenergy beam” is the movement of the second energy beam that an observermoving with the first energy beam would “see”. This relative movement ofthe second energy beam with respect to the first energy beam can beimplemented by a separate, for example first energy beam movement unit,examples of which will be given later.

The combination energy beam is then moved across the build field by asecond energy beam movement unit, for example a conventional scannermirror when using laser beams. In other words, the relative positioning(of the intensity distribution) of the second energy beam in thecombination energy beam (or within its intensity distribution) isachieved only by this first energy beam movement unit. The second energybeam movement unit moves the common area of incidence of the energybeams, i.e. the area of incidence of the combination energy beam (whichin this respect could also be called a “unit beam”), and the combinationenergy beam changes its overall intensity distribution accordingly dueto the movement of the second energy beam relative to the first energybeam.

In a preferred variant in this regard, it is simply ensured that thebeam path of the first energy beam and a “virtual beam path” of thesecond energy beam run coaxially in order to be moved over the materialin a coordinated manner as a superimposed combination energy beam. This“virtual beam path” (or “virtual beam axis”) of the second energy beammoved relative to the first energy beam is defined as running throughthe geometric centre of gravity of a “virtual section plane area ofincidence” lying in a section plane (as defined above) perpendicular tothe (virtual) beam axis, with the “virtual section plane area ofincidence” being defined by the area in the section plane which thesecond energy beam sweeps over with its spatial extent determined by itsparticular intensity distribution during a defined period of time. Thedefined time period is preferably at least long enough for the secondenergy beam to have passed through a movement cycle, particularlypreferably a number of movement cycles, in a (preferred) repeatingmovement pattern. In this case, the time period is particularlypreferably exactly one period (duration of a movement cycle) or aninteger multiple of a period. In the case of a second energy beamcirculating in a circular manner relative to the first energy beam, forexample, the “virtual beam path” of the second energy beam could thusalso be regarded as an “averaged beam path” or “averaged beam axis”,which results when the position of the actual beam axis of the secondenergy beam, which moves relative to the beam axis of the first energybeam, is integrated over a certain integration time period as mentioned.

On the path of the common beam path, i.e. after the combination of thefirst energy beam and the second energy beam moving relative theretoaccording to the invention, the two energy beams pass through the samebeam-deflecting or beam-modifying optical components as a combinationenergy beam on their respective paths.

An irradiation device usable for this purpose for irradiating a materialaccordingly has an energy beam source system, for example preferably alaser system, for generating at least the first energy beam and thesecond energy beam, wherein this energy beam source system can againhave different energy beam sources for the different energy beams, oralso beam splitters etc. Further, the irradiation device has a firstenergy beam movement unit for moving the second energy beam relative tothe first energy beam, an energy beam combination device, and a secondenergy beam movement unit, which are formed and arranged relative toeach other such that the first energy beam and the second energy beammoving relative thereto are coupled in a common beam path into thesecond energy beam movement unit in such a way that they are movedtogether as a combination energy beam by the second energy beam movementunit over the material or build field.

The energy beam combination device for coupling the first energy beamand the second energy beam moving relative thereto into the common beampath can comprise a beam combiner which is arranged downstream of thefirst energy beam movement device (i.e. downstream in the beamdirection) and upstream of the second energy beam movement unit (i.e.upstream in the beam direction) in order to couple the first energy beamand the second energy beam, for example parallel to each other, forexample with beam paths with a small spacing in relation to the beamextent or diameter of one of the beams, as will be explained below withreference to examples, into the second energy beam movement unit, forexample onto the first scanner mirror of a conventional scanner system.

The beam combiner preferably has or can be formed by a polariser,particularly preferably a thin-film polariser.

When the energy beams or intensity distributions moved relative to eachother are coupled into the common beam path by the second energy beammovement unit, it can be ensured that the optical components of thesecond energy beam movement unit, i.e. for example the scanner, as wellas any subsequent components that may influence the direction of theenergy beams, such as a coupling window in a construction space (processchamber) of a manufacturing device, have only negligible influence onthe overall intensity distribution of the combination energy beam.

In particular, it would therefore also be possible to retrofit existingmanufacturing devices with an irradiation device according to theinvention, so the existing energy beam movement units, i.e. scanners forexample, could continue to be used as second energy beam movement unitswithin the scope of the invention without any modifications.

A manufacturing device can then correspondingly have at least one suchirradiation device which is constructed in accordance with the inventionor has been modified in accordance with the invention by retrofitting.It is also possible to retrofit existing manufacturing devices with anirradiation device according to the invention as a complete module or toreplace the existing irradiation devices accordingly. This is alsopossible for manufacturing devices that work with a plurality ofseparate energy beams in order to solidify material in parallel at anumber of positions on the build field. In this case, only individual,but also several—for example all—energy beams can be generated bycorresponding irradiation devices.

Preferably, within the irradiation method, the second energy beam isintensity modulated (i.e. an intensity of the second energy beam ismodulated) in dependence of its relative position to the first energybeam or in dependence of the current position in the combination energybeam, i.e. during the relative movement. Alternatively or additionally,the second energy beam can also be intensity modulated as a function ofa current direction of movement of the combination energy beam on thematerial or build field, i.e. the current scanning direction, i.e. as afunction of a direction of movement of a corresponding element of theenergy beam movement unit(s), for example a scanner mirror. This isindependent of where the two energy beams are combined or superimposedon each other, for example already before coupling into a common energybeam movement unit or only on or before impingement on the build field.

In principle, however, an intensity of the first energy beam could alsobe modulated.

In intensity modulation it is preferred that the minimum intensity is atleast always greater than 0, i.e. that the second energy beam within thecombination energy beam always contributes to an increase in the overallintensity at the particular location in the overall intensitydistribution of the combination energy beam.

An intensity modulation makes it possible to generate combination energybeams whose (time-integrated) overall intensity distribution has, forexample, an absolute maximum and/or an absolute minimum only at a singleposition and, if necessary, local maxima and/or minima at furtherpositions in the overall intensity distribution with respect to theparticular environment or in a specific intersection direction or alonga specific intensity profile curve, so that the overall intensitydistribution has the above-mentioned features according to theinvention.

Preferably, the energy beam source system of the irradiation device isthen designed and/or the irradiation device has an energy beammodulation unit such that the second energy beam is intensity modulatedin the desired manner. For this purpose, the irradiation device can havea control device which controls the energy beam source system, inparticular the second energy beam source, if this is operated separatelyfrom the first energy beam source, and/or the energy beam modulationunit accordingly.

In principle, the first energy beam and the second energy beamthemselves can have any intensity distributions. Preferably, they havequalitatively and/or quantitatively different intensity distributions,very particularly preferably not only quantitatively but alsoqualitatively, i.e. completely different forms. What is decisive is thatultimately the (time-integrated) overall intensity distributiongenerated in this way has the above-mentioned features according to theinvention.

In a particularly preferred variant, the first energy beam has anintensity distribution that is substantially rotationally symmetrical(i.e. within the usual tolerances) with respect to a beam axis.

The first energy beam particularly preferably has a so-called “top-hat”or “flat-top” intensity distribution. Such an intensity distribution ischaracterised in that it has a spatially relatively homogeneousintensity distribution across the beam cross-section, i.e. a relativelysmooth, flat surface with a relatively sharp edge. In cross-sectionthrough the beam axis, such a “top-hat” or “flat-top” intensitydistribution shows a rectangular profile. Such a profile can bedescribed by a Heaviside function (step or jump function).

With a top-hat intensity distribution, a defined relatively homogeneousbasic intensity can be ensured within the combination energy beam, i.e.within the overall intensity distribution. Moreover, suitablebeam-shaping units are already available for such top-hat intensitydistributions, for example diffractive optical elements (DOEs).

Particularly preferably, the second energy beam also has an intensitydistribution that is substantially rotationally symmetrical with respectto a beam axis, i.e. within the usual tolerances. This second energybeam can, for example, particularly preferably have a Gaussian intensitydistribution. Such a Gaussian intensity distribution usually does notrequire beam shaping, since most energy beam sources, in particularlasers, as mentioned, already generate a beam with a Gaussian intensitydistribution.

By combining a first energy beam with a top-hat intensity distributionto provide the homogeneous basic intensity in the overall intensityprofile and a second energy beam with a Gaussian intensity distributionmoving very fast relative to it within the overall intensitydistribution, almost any overall intensity distributions can begenerated within the combination energy beam.

Preferably, the second energy beam is “smaller” or “finer” than thefirst energy beam, i.e. the second energy beam has a smaller maximumbeam extent than the first energy beam, especially when it is coupledinto the common beam path by the energy beam movement unit (i.e. at thecoupling point, for example on the first scanner mirror of aconventional scanner system).

A beam extent in this sense is understood to mean any dimension ordistance transverse (to the beam axis) through the beam, that is to sayfor example a beam diameter or a beam width, with a beam width alwaysbeing understood to mean the extent perpendicularly to the currentdirection of movement of the area of incidence on the build field. Thedistance does not necessarily have to run through the beam axis or thecentre of the (overall) intensity distribution, especially if the energybeam does not have a rotationally symmetrical intensity distribution.The beam extent is defined here in such a way that it runs along thedefined path from an edge—as defined above—(i.e. that 99% of the radiantpower of the energy beam is within the area enclosed by the edge) to theopposite edge of the intensity distribution.

For example, the beam extent of the first energy beam may be at least500 μm, preferably at least 700 μm, further preferably at least 900 μm,even further preferably at least 1000 μm, even further preferably atleast 1100 μm, even further preferably at least 1200 μm, even furtherpreferably at least 1500 μm, particularly preferably at least 2 mm.Alternatively or additionally, the maximum beam extent of the firstenergy beam is at most 10 mm, preferably at most 6 mm, furtherpreferably at most 4 mm, particularly preferably at most 3 mm.

The beam extent of the second energy beam, which is moved relative tothis first energy beam or is preferably moved within the beam extent ofthe first energy beam, is at least 20 μm, preferably at least 50 μm,particularly preferably at least 80 μm. However, this maximum beamextent of the second energy beam is at most 300 μm, preferably at most200 μm, particularly preferably at most 100 μm.

A ratio of the beam extent of the second energy beam to the beam extentof the combined energy beam and/or the first energy beam is in this casepreferably at most 1:3, further preferably at most 1:5, even furtherpreferably at most 1:10, even further preferably at most 1:20.

In the case of a substantially circular shape of the first and second aswell as the combined energy beam, the ratio of the diameter of thesecond energy beam to the diameter of the combined energy beam and/or tothe diameter of the first energy beam is preferably at least 1:100,particularly preferably at least 1:50.

Very particularly preferred is a combination in which the beam extent,for example a diameter, of the first energy beam and thus also the beamextent or diameter of the combination energy beam is 1000 μm (with atop-hat intensity distribution) and the second energy beam (with aGaussian intensity distribution) has a beam extent, for example a beamdiameter, of 80 μm.

Preferably, as mentioned, the relative movement of the second energybeam with respect to the first energy beam takes place cyclically, i.e.the same position is repeatedly approached by the second energy beamwithin the combination energy beam on a closed curve. In particular, inthe case of a straight, purely translatory scanning movement of thecombination energy beam, the same position (relative to the first energybeam) is particularly preferably passed at equal time intervals duringthe relative movement of the second energy beam.

Additionally or alternatively, the intensity is also cyclicallymodulated accordingly by controlling the power of the second energybeam. For example, the control signal for intensity modulation of thesecond energy beam, preferably a generator signal for a second energybeam source which generates the second energy beam, can be formed as asinusoidal signal or similar. In this way, a cyclic intensity modulationis automatically achieved.

The intensity modulation is particularly preferably carried out with asmooth and periodic control signal. Preferably, the function of thecontrol signal corresponding to the above-mentioned function of theintensity values along the intensity profile curve can be differentiatedat least once at each point, further preferably can be differentiated atleast twice, particularly preferably can be differentiated any number oftimes. An ideal target control signal can, for example, be approximatedor exactly mapped by trigonometric functions such as a sine or cosinesignal or a linear combination of trigonometric functions. Similarly,any other control program or algorithm that periodically repeats afunction defined over a revolution (for example from −π to +π) couldalso be used.

A possible generator signal to modulate the second energy beam could,for example, be described by means of the following function:

${u(t)} = {{A\;{\cos\left( \frac{{\omega\; t} + {\theta(t)}}{2} \right)}^{2n}} + c}$

Here, A is the difference between the local minimum value and the localmaximum value, w stands for the angular velocity of a rotation of thesecond energy beam about its virtual rotation axis, t denotes the time,θ(t) denotes the above-mentioned (time-dependent) phase shift for ashift of the minima and maxima on the intensity profile curve, thenumber n in the exponent is a natural number, and c represents aconstant. By increasing the exponent n the intensity profile curve canbe made to slope more steeply from the local maximum value to bothdirections.

A shift in the maximum and minimum values of the intensity of the secondenergy beam along its (relative) path of movement can be achieved by aphase shift of the periodic control signal.

The first energy beam source and/or the first energy beam movement unitand/or an energy beam modulation unit can be designed and controlledaccordingly by a control device to ensure such a cyclic relativemovement or intensity modulation.

Particularly preferably, the relative movement and/or the intensitymodulation of the second energy beam take place uniformly, in particularduring a straight, purely translatory scanning movement of thecombination energy beam. With regard to the relative movement, thismeans that the amount of the relative speed remains the same and doesnot change during the movement, but only the direction of movement; withregard to the intensity modulation, this means that the modulation isstepless.

Very particularly preferably, the second energy beam moves along theedge of the intensity distribution of the first energy beam. Preferably,this is done in such a way that at least one maximum of the intensitydistribution, i.e. the centre in the case of a Gaussian profile, of thesecond energy beam moves within an area of the first intensitydistribution bounded by the edge. Particularly preferably, it is ensuredthat the edge of the overall intensity distribution of the combinationenergy beam substantially coincides with the edge of the intensitydistribution of the first energy beam, or that they are at leastrelatively close to each other, for example <20 μm, so that the overalldiameter of the combination energy beam is substantially defined by thediameter of the first energy beam. Preferably, the dimensionaldifference between the edge of the overall intensity distribution of thecombination energy beam and the edge of the intensity distribution ofthe first energy beam is at most approximately 40%, further preferablyat most approximately 25%, particularly preferably at most approximately15%, of a beam extent of the second (“smaller”) energy beam. Preferably,at least one maximum of the intensity distribution of the second energybeam lies within the intensity distribution of the first energy beam.

Preferably, the second energy beam moving relative to the first energybeam contributes 99% of its energy in the edge region of the overallintensity distribution.

This procedure, in which the second energy beam is moved along acircular path along the edge or within the edge of the intensitydistribution of the first energy beam, is particularly preferred if thefirst energy beam has a rotationally symmetrical or circular intensitydistribution and very particularly preferably a top-hat intensitydistribution.

A combination energy beam generated in this way then exhibits—withsuitable intensity modulation of the first energy beam with a sinusoidalsignal adapted to the period of the cyclic relative movement—a(time-integrated) overall intensity distribution that satisfies thecriteria according to the invention given above.

In order to achieve such a relative movement of the second energy beamrelative to the first energy beam along a closed path, in particular acircular path, in the case of an optical energy beam, for example alaser beam, a rotating optical element, for example a beam shift elementor a reflector, in particular a so-called flat plate and/or a mirror,can preferably be used. That is to say, the first energy beam movementunit preferably comprises a rotating unit with a suitable rotatableoptical element. This optical element may, for example, be driven by asuitable motor, and the rotation may be relatively fast, namely suchthat, in terms of magnitude, the desired fast rotation or movement ofthe second energy beam relative to the scanning speed is achieved. Forexample, the rotation of the optical element could take place with aradius of a circular movement of a second energy beam running parallelto the virtual beam axis of 2 mm and a movement speed (that is to sayits path speed on its cyclic path) of 5 m/s with approximately 400revolutions per s, with a movement speed of the second energy beam of 31m/s with approximately 2500 revolutions per s, with a movement speed ofthe second energy beam of 50 m/s with approximately 4000 revolutions pers.

Preferably, the beam path of the second energy beam can thus bedeflected by such a rotation unit with a rotatable optical element andfurther optical elements of the energy beam movement unit in such a waythat it rotates on a “virtual cylinder surface” about a “virtualrotation axis” and always runs parallel to this virtual rotation axis.This virtual rotation axis then corresponds to the virtual beam axisdefined above or the virtual beam path of the second energy beam.

There are various possibilities for the specific realisation of suchrotation units. Examples of this will be given later.

Preferably, the energy beam movement unit is designed in such a way thatthe distance between the actual beam axis and the virtual beam axis ofthe second energy beam, i.e. the diameter of the “virtual cylindersurface”, is adjustable.

Preferably, the control data are generated with determination of furtherprocess parameters (in addition to the intensity distribution of theenergy beam or combination energy beam) and optionally according to theparticular position of the area of incidence in the component in such away, i.e. the intensity distribution, that is to say the beam extentand/or “shape” at the area of incidence of the energy beam on the buildfield, and further process parameters are optimised and determined insuch a way, that when the device is controlled using said control data,a melting of the build-up material within a target region in and aroundthe area of incidence is effected by means of heat conduction welding. A“target region” in this context means on the one hand the area ofincidence, i.e. the region in which the energy beam impinges on thesurface, but also the region below it, i.e. into the depth of thematerial or the layer, and possibly also an environment around this areaof incidence in which the energy beam still has an effect, e.g. due toheat conduction in the build-up material.

These further process parameters can include, for example, the absolutebeam intensity, the speed of movement of the area of incidence on thebuild field, i.e. the scanning speed, but also the layer thickness andthe exact irradiation strategy, i.e. for example in which pattern theirradiation takes place. Likewise, other diverse parameters can be takeninto account, in particular material characteristics of the build-upmaterial, and certain optimisation criteria and/or secondary conditionsand/or constraints can be defined in order to then calculate an optimallocal target temperature distribution in the target region in which thebuild-up material is to be melted and, in turn, the optimal (ifnecessary, also time-integrated overall) intensity distribution, fromwhich the control data for controlling the irradiation device and/orfurther components of the manufacturing device for additivemanufacturing are then generated and used in the manufacturing process.

Preferably, the (overall) intensity distribution of the energy beam orcombination energy beam (if this is generated by superimposing energybeams) can be monitored and/or controlled. Particularly preferably, thedata acquired during the monitoring and/or control are used for acontrol of the (overall) intensity distribution, for example as anactual intensity distribution, which can be compared with a targetintensity distribution.

Accordingly, the irradiation device preferably has a suitable monitoringand/or control device (hereinafter also referred to as the “monitoringdevice”).

Such a monitoring device can be realised, for example, with the aid of abeam splitter arranged in the beam path of the energy beam orcombination energy beam, which beam splitter, for example, branches offa small part of the intensity of the (combination) energy beam into amonitoring unit for measuring and checking the (overall) intensitydistribution of the (combination) energy beam. The monitoring unit can,for example by means of an area sensor or the like, acquire an integralimage/signal of the (overall) intensity distribution.

Insofar as a combination energy beam is to be monitored, which isgenerated by superimposing energy beams, the “exposure time” of the areasensor is preferably adapted to the integration time period definedabove and/or an incomplete exposure of the sensor (at least one completerotation of the second energy beam as well as a fraction of one or morefurther revolutions) is compensated for by a filter, for example anevaluation algorithm.

In the context of a monitoring of the (overall) intensity distribution,an actual intensity distribution, for example, an actual rotation of theoverall intensity distribution can be compared with a target rotationand/or an actual distribution can be compared with a target distributionof the (overall) intensity distribution. By means of an additionalcontrol loop, the actual setting in question can be readjusted ifnecessary.

The invention is explained in greater detail below with reference to theaccompanying figures on the basis of embodiment examples. In the variousfigures, like components are provided with like reference numbers. Inthe figures:

FIG. 1 shows a schematic, partially sectional view of an embodimentexample of an additive manufacturing device with an energy beammodification device usable for the invention,

FIG. 2 shows a perspective view of an embodiment example of a preferred(overall) intensity distribution of a combination energy beam accordingto the invention,

FIG. 3 shows a longitudinal section along the section plane B throughthe overall intensity distribution according to FIG. 2,

FIG. 4 shows a schematic representation of the functional arrangement ofthe components of a first embodiment example of an irradiation deviceusable for the invention,

FIG. 5 shows a schematic representation of the functional arrangement ofthe components of a second embodiment example of an irradiation deviceusable for the invention,

FIG. 6 shows a schematic representation of the functional arrangement ofthe components of a third embodiment example of an irradiation deviceusable for the invention,

FIG. 6a shows an enlarged schematic representation of the first energybeam movement unit of the irradiation device according to FIG. 6,

FIG. 7 shows a representation of a possible control signal forcontrolling a second energy beam source in an irradiation device,

FIG. 8 shows a (overall) intensity distribution of a combination energybeam according to the invention as in FIG. 2 in a perspective plan view,but for comparison in three different embodiments, to show thedependence of the overall intensity distribution on the control signalaccording to FIG. 5,

FIG. 9 shows a greyscale image of a (overall) intensity distributionaccording to the invention at the area of incidence of a combinationenergy beam as shown in FIG. 7 on the right,

FIG. 10 shows a schematic representation for the modification of a(overall) intensity distribution according to the invention as afunction of an area of incidence environment parameter,

FIG. 11 shows a further schematic representation for the modification ofa (overall) intensity distribution according to the invention as afunction of an area of incidence environment parameter,

FIGS. 12a to 12e are each perspective views of alternative embodimentexamples of intensity distributions according to the invention.

The following embodiment examples are described with reference to adevice 1 for the additive manufacture of manufacturing products in theform of a laser sintering or laser melting device 1, it being explicitlypointed out once again that the invention is not limited to lasersintering or laser melting devices. The device will therefore bereferred to in the following—without any limitation of generality—as a“laser sintering device” 1 for short.

Such a laser sintering device 1 is shown schematically in FIG. 1. Thedevice has a process chamber 3 or a process area 3 with a chamber wall4, in which the manufacturing process fundamentally takes place. Anupwardly open container 5 with a container wall 6 is located in theprocess chamber 3. The upper opening of the container 5 in each instanceforms the current working plane 7. The region of this working plane 7located within the opening of the container 5 can be used to build theobject 2 and is therefore referred to as the build field 8.

The container 5 has a base plate 11 which is movable in a verticaldirection V and is arranged on a support 10. This base plate 11 closesthe container 5 at the bottom and thus forms its base. The base plate 11may be formed integrally with the support, but it may also be a plateformed separately from the support 10 and fixed to the support 10 orsimply mounted thereon. Depending on the type of specific build-upmaterial, for example the powder used, and the manufacturing process, abuild platform 12 may be attached to the base plate 11 as a build baseon which the object 2 is built. In principle, however, the object 2 canalso be built on the base plate 11 itself, which then forms the buildingbase.

The basic construction of the object 2 is achieved by first applying alayer of build-up material 13 to the build platform 12, then—asexplained later—selectively solidifying the build-up material 13 byirradiating it with a laser at the points which are to form parts of theobject 2 to be manufactured, then lowering the base plate 11, thus thebuild platform 12, with the aid of the support 10, and applying a newlayer of build-up material 13 and then selectively solidifying it. Thisprocess is repeated until all layers of the at least one object aresolidified. In FIG. 1, the object 2 built in the container on thebuilding platform 12 is shown below the working plane 7 in anintermediate state. It already has a number of solidified layers,surrounded by build-up material 13 which has remained unsolidified.Various materials can be used as build-up material 13, preferablypowder, in particular metal powder, plastic powder, ceramic powder,sand, filled or mixed powder or also pasty materials.

Powdery build-up material 13 is located in a storage container 14 of thelaser sintering device 1. With the aid of a coater 16 movable in ahorizontal direction H, the build-up material can be applied in theworking plane 7 or within the build field 8 in the form of a thin layer.

Optionally, an additional radiation heater 17 is located in the processchamber 3. This can be used to heat the applied build-up material 13 sothat the irradiation device used for the selective solidification doesnot have to apply too much energy. This means that, for example, aquantity of basic energy can already be introduced into the build-upmaterial 13 with the aid of the radiation heater 17, which energy is ofcourse still below the necessary energy at which the build-up material13 sinters or even melts. An infrared radiator, for example, can be usedas the radiation heater 17.

For selective solidification, the laser sintering device 1 has, asmentioned, an irradiation device 20 or, in this case specifically, anexposure device 20. This irradiation device 20 generates here, as outputlaser beam AL, a combination energy beam AL (or in the following alsoreferred to as a combination laser beam AL) with a defined modifiableoverall intensity distribution GIV (see for example FIG. 2) by combiningtwo energy beams EL1, EL2 and moving the energy beams EL1, EL2 relativeto each other by means of a first energy beam movement unit 30, as willbe explained in greater detail later.

The combination energy beam AL is then deflected via a subsequent secondenergy beam movement unit 23 (also referred to as a deflection unit 23or scanner 23) in order to travel along the exposure paths or tracksprovided in accordance with the exposure strategy in the layer to beselectively solidified and in order to selectively introduce the energy.In other words, by means of the scanner 23, the area of incidence AF ofthe combination energy beam AL on the build field 8 is moved, and thecurrent movement vector or the direction of movement S (scanningdirection) of the area of incidence AF on the build field 8 can changefrequently and rapidly. In so doing, this laser beam AL is focused onthe working plane 7 in a suitable manner by a focusing device 24.

Specifically, the irradiation device 20 here comprises an energy beamsource system 21 or laser system 21 for generating a first laser beamEL1 and a second laser beam EL2 by two separate lasers 21 a, 21 b.Downstream of the laser 21 b for the second laser beam EL2, theirradiation device 20 has a first energy beam movement unit 30 formoving the second laser beam EL2 relative to the first laser beam EL1,and an energy beam combination device 22, which is formed and arrangedrelative to the scanner 23 such that the first laser beam EL1 and thesecond laser beam EL2 are coupled into a common beam path in the scanner23 such that they are moved together as a combination energy beam ALover the material 13 or the build field 8. For details regarding theconstruction of the irradiation device 20, reference is made to FIGS. 4and 5 with their respective explanations.

Preferably, the lasers 21 a, 21 b may be gas or solid-state lasers orany other type of laser, such as laser diodes, in particular VCSEL(Vertical Cavity Surface Emitting Laser) or VECSEL (Vertical ExternalCavity Surface Emitting Laser) or a line of these lasers. Veryparticularly preferably, one or more single-mode lasers, for example afibre laser with a power of 3 kW and a wavelength of 1070 nm, may beused within the scope of the invention. The lasers 21 a, 21 b for thefirst and second laser beams EL1, EL2 can be identical, but can also beconstructed differently.

The irradiation device 20 is here preferably located outside the processchamber 3, and the combination laser beam AL is directed into theprocess chamber 3 via a coupling window 25 arranged on the upper side ofthe process chamber 3 in the chamber wall 4.

It should be noted, however, that the invention is not limited to thefact that the energy beam AL with the intensity distribution GIVaccording to the invention, which ultimately impinges on the build field8, is generated as a combination energy beam AL by superimposingindividual energy beams EL1, EL2, which are moved relative to eachother, but that an energy beam AL with an intensity distribution GIVaccording to the invention could also be generated with the aid ofanother irradiation device. Nevertheless—without limiting thegenerality—the following is based on the example of superimposing twoenergy beams or laser beams EL1, EL2 to generate a combination energybeam AL with a (time-integrated) desired overall intensity distributionGIV.

The laser sintering device 1 further contains a sensor arrangement 18which is suitable for detecting process radiation emitted during theimpingement of the laser beam 22 on the build-up material in the workingplane. This sensor arrangement 18 operates here in a spatially resolvedmanner, i.e. it is able to detect a type of emission image of theparticular layer. Preferably, an image sensor or a camera 18 which issufficiently sensitive in the range of the emitted radiation is used asthe sensor arrangement 18. Alternatively or additionally, one or moresensors for detecting an electromagnetic, in particular optical and/orthermal process radiation could also be used, for example photodiodeswhich detect the electromagnetic radiation emitted by a weld pool underimpinging laser beam AL, or temperature sensors for detecting an emittedthermal radiation. It would be possible to assign the signal of asensor, which itself does not have spatial resolution, to thecoordinates by assigning the coordinates, which are used to drive thelaser beam, to the sensor signal, in each case in terms of time. In FIG.1, the sensor arrangement 18 is located inside the process chamber 3.However, it could also be located outside the process chamber 3 andcould then detect the process radiation through another window in theprocess chamber 3.

The signals detected by the sensor arrangement 18 are transferred hereas a process area sensor data set or layer image SB to a control device50 of the laser sintering device 1, which is also used to control thevarious components of the laser sintering device 1 for overall controlof the additive manufacturing process.

For this purpose, the control device 50 has a control unit 51 whichcontrols the components of the irradiation device 20 via an irradiationcontrol interface 53, namely in this case transmits laser control dataLSa, LSb to the lasers 21 a, 21 b, transmits relative movement controldata RS to the first energy beam movement unit 30, transmits scancontrol data SD to the second energy beam movement unit 23 or thescanner 23, and transmits focus control data FS to the focusing device24.

The control unit 51 also controls the radiation heater 17 by means ofsuitable heater control data HS, controls the coater 16 by means ofcoating control data ST, and controls the movement of the support 10 bymeans of support control data TS.

In addition, the control device 50 here has a quality data determinationdevice 52, which receives the process space sensor data set SB anddetermines quality data QD based thereon, which quality data can betransferred to the control unit 51, for example, in order to be able tointervene in the additive manufacturing process in a regulating manner.

The control device 50 is coupled, here for example via a bus 55 oranother data connection, to a terminal 56 with a display or the like.Via this terminal 56, an operator can control the control device 50 andthus the entire laser sintering device 1, for example by transmittingprocess control data PST.

In order to adjust the production process so that the process is carriedout, for example, as a heat conduction welding process and not as a deepwelding process, the control data can be generated or modified by meansof a control data generation device 54, 54′.

This control data generation device 54 can, for example, be part of thecontrol device 50 and be implemented there, for example, in the form ofsoftware components. Such a control data generation device 54 integratedin the control device 50 can, for example, take over the process controldata PSD and modify it accordingly so that an energy beam AL with thedesired intensity distribution GIV is generated, and can then transmitthe correspondingly modified control data PSD to the control unit 51.The modified control data PSD can in particular be modified lasercontrol data LSa, LSb, but possibly also other modified control data,such as modified coating control data ST or support control data TS, inorder to select a suitable layer thickness. Alternatively, only thelaser control data LSa, LSb could be modified in the control datageneration device 54 and transferred to the control unit 51 so that theirradiation control interface 53 operates with the modified lasercontrol data LSa, LSb.

However, it would also be possible for the control data generationdevice 54′ to be implemented on an external computer unit, for examplehere the terminal 56, and to already create process control data PSDwith correspondingly suitable exposure control data in advance, withwhich the device 1 is controlled in such a way that the desiredintensity distribution GIV is achieved. In this case, the internalcontrol data generation device 54 present here in the control device 50could also be dispensed with.

As already mentioned, the process control data PSD generated or modifiedby the control data generation device 54, 54′ can also be regarded astarget values which are then used in the control unit 51 for a controlprocess; for example (as one possibility), the quality data QD can beincluded as actual values.

It is noted once again at this juncture that the present invention isnot limited to such a laser sintering device 1. In particular, it can beapplied to any other methods for generative or additive production of athree-dimensional object by depositing and selectively solidifying abuild-up material, in particular layer by layer, wherein an energy beamfor solidification is emitted onto the build-up material to besolidified. Similarly, it could be used for the welding of weld seams orfor other processes in which material is to be irradiated with an energybeam, in particular for local melting of the material. Accordingly, theirradiation device can also not only be a laser, as described herein,but any device could be used with which energy can be selectivelybrought onto or into the build-up material in the form of wave orparticle radiation. For example, instead of a laser, another lightsource, an electron beam, etc. could be used. Likewise, a number ofcombination energy beams according to the invention can be generated andused in parallel, for example in order to be able to selectivelysolidify material at a number of positions in the build field at thesame time.

Even though only a single object 2 is shown in FIG. 1, it is possibleand usually also customary to produce a number of objects in parallel inthe process chamber 3 or in the container 5. For this purpose, thebuild-up material is scanned layer by layer by the energy beam at pointswhich correspond to the cross sections of the objects in the particularlayer.

FIG. 2 shows the typical basic form of an overall intensity distributionGIV of a combination energy beam AL, which would be particularly wellsuited for use in this form or in a somewhat modified form (see also thelater explanations regarding FIG. 2 and FIG. 7) in order to keep themelting process of the build-up material 13 in the region of the area ofincidence AF of the combination energy beam AL on the build field 8within the process region of heat conduction welding, i.e. without avapour capillary being formed as the build-up material melts. Theoverall intensity distribution GIV of this combination energy beam ALfulfils in particular the conditions according to the invention asdefined above.

FIG. 2 shows the overall intensity distribution GIV (hereinafter alsoreferred to as the intensity distribution GIV for short) in a plane x, yperpendicular to the beam axis SA of the combination energy beam AL(hereinafter also referred to merely as an energy beam AL for short),with the intensity in the z-direction being spatially resolved andplotted above this plane x, y. Depending on the angle of incidence ofthe energy beam AL on the build field 8, slight distortions may occur,which, however, could also be compensated in principle during thegeneration of the energy beam AL by corresponding control of theindividual components, if this is necessary and/or desired.

In a middle region of the overall intensity distribution GIV, i.e. hereapproximately within half the radius to the edge R of the intensitydistribution GIV (which is defined as above so that 99% of the radiantpower lies inside the edge R), there is an intensity minimum MIZ (alsoabbreviated hereinafter as the “minimum”). This minimum MIZ lies hereapproximately in the centre of the intensity distribution GIV, i.e.approximately on the beam axis SA or the axis of the beam path of theenergy beam AL.

In an edge region running around this middle region, i.e. along anintensity profile curve IPK running around inside the edge R, but alongthe edge, there is a local intensity maximum value MAX (hereinafter alsoabbreviated as “maximum value”) on one side with respect to thisintensity profile curve IPK and a local intensity minimum value MIN(hereinafter also abbreviated as “minimum value”) diagonally opposite.“Local” is to be understood here in each instance in relation to thefunction of the intensity values over the locations along the intensityprofile curve IPK, which runs parallel to the edge R or concentricallyon a circumferential circular path K.

The intensity values on the intensity profile curve IPK along thecircular path K run continuously here from the intensity maximum MAX onboth sides, i.e. in both directions of rotation, towards the intensityminimum MIN, i.e. they decrease (here continuously) until there.Depending on the type of signal generation, the signal could also besubject to so-called “ringing” or other effects, such as digitisationstages, which could manifest themselves in the intensity profile curveas noise, harmonics, or in the form of other artefacts. The intensitydistribution GIV is oriented here in such a way that the maximum valueMAX on the intensity profile curve IPK in the scanning direction S (herearbitrarily parallel to the x-direction of the plane) is at the frontand the minimum value MIN is at the back.

FIG. 3 shows a longitudinal section through this overall intensitydistribution GIV in a section plane B extending in the scanningdirection S (i.e. in the x/z direction), as shown in FIG. 2. In FIG. 2,the same longitudinal section as in FIG. 3 is shown in simplified formin the section plane B for illustration purposes.

Here, too, the maximum MAX is clearly visible at the front in thescanning direction S and the minimum MIN at the rear end, which,however, again forms a local maximum in relation to its surroundingsalong the longitudinal section in FIG. 3, since the intensity of theintensity distribution GIV drops sharply outwardly towards the edge Rand the minimum MIZ is located in the middle, i.e. towards the centre.

In order to explain the advantageous effect of the intensitydistribution GIV for setting a certain target temperature in the buildfield 8 in the region of the area of incidence, at which temperature itis possible to keep the melting process within the process window of theheat conduction welding, the intensity distribution GIV is dividedvirtually into three functional regions F1, F2, F3 (see FIG. 3) in thefollowing. The entire intensity distribution GIV basically determines an“effective range”, which may be limited, for example, by the edge R ofthe intensity distribution GIV, but may also extend somewhat beyond it.These terms can be defined as follows:

The overall intensity distribution GIV impinges on an area of incidenceAF, which is moved on a build field 8, as has already been explained anumber of times above. At least in partial regions of the area ofincidence AF of the combination energy beam AL, a melting of thebuild-up material 13 is caused. In order to achieve the process windowof heat conduction welding in the melting region as far as possible, theoverall intensity distribution GIV must be adjusted in such a way thatit fulfils various tasks.

In the following description, it is assumed that the observer moves withthe area of incidence AF. From the observer's point of view, newmaterial 13 is transported into the area of incidence AF at any timeduring the movement of the area of incidence AF on the build field 8.This build-up material 13 is usually colder than the weld pool.Therefore, the build-up material 13 must first be heated. This task isperformed by a first functional region F2 “heat”, which generally hasthe highest intensities of all differentiated functional regions F1, F2,F3 of the intensity distribution GIV. In FIG. 3 this is, accordingly,the front region of the intensity distribution GIV with the absolutemaximum MAX. Here, it is evident wherever the intensity distribution GIVin the movement over the build-up material first encounters unsolidifiedbuild-up material or build-up material that has solidified in the courseof an earlier irradiation or melting process.

At the edge of the area of incidence AF, heat is transported away mainlyby conduction into the surrounding build-up material 13. These lossesshould preferably be compensated. This compensation can be realised inthe preferred intensity distribution GIV by the functional region F1“hold”. This functional region F1 “hold” forms a kind of (in plan viewlateral) border of the entire intensity distribution GIV and ischaracterised in FIGS. 2 and 3 by an increase in intensity compared tothe immediately adjacent area of incidence. In other words, this is thecircular region of increased intensity running along the edge R insidethe edge over the intensity profile curve IPK.

In the region lying in front in the scanning direction S, thisfunctional region F1 “hold” merges into the functional region F2 “heat”.Since after passing the area of incidence AF on the build field 8 thebuild-up material 13 is to harden again locally, it makes sense that theminimum MIN is located in the functional region F1 “hold” on theintensity profile curve IPK in the rear region in the scanning directionS.

The region of the overall intensity distribution GIV, which issurrounded by the functional regions F1, F2 “hold” and “heat”, has thetask of setting the temperature profile in the effective region, i.e. inthe melt, and controlling it in such a way that, for example, thedesired process region of the heat conduction welding can be maintained.This is performed by the functional region F3 “shape”.

The transition between the functional regions F1, F2, F3 is continuous,and the functional regions F1, F2, F3 can overlap or superimpose in someareas. As can be seen here, the intensity distribution GIV in thefunctional region F3 “shape” is basically a (flat) convex function,whereas the other functional regions F1, F2 have a concave functioncurve in cross section.

Such a preferred overall intensity distribution GIV can be achieved, asalready described above, by a combination energy beam AL, which isgenerated from two energy beams EL1, EL2 by superimposition, with theenergy beam EL2 being moved at a high velocity in terms of magnituderelative to the first energy beam EL1, in relation to the magnitude ofthe scanning velocity.

The (overall) intensity distribution shown in FIGS. 2 and 3 can beachieved quite specifically by generating a first energy beam EL1 with afirst intensity distribution SP1, which corresponds to a so-calledtop-hat-shaped intensity distribution SP1, and substantiallysuperimposing on this a Gaussian-shaped second intensity distributionSP2 of the second energy beam EL2 running around over the circular pathK along the edge R of the intensity distribution SP1 of the first energybeam EL1. In this case, the beam extent, here the diameter, of theintensity distribution SP2 of the second energy beam EL2 is considerablysmaller than the beam extent DS, here the diameter DS, of the intensitydistribution SP1 of the first energy beam EL1. For example, the firstenergy beam EL1 may have a diameter of approximately 1000 μm, and thesecond energy beam EL2 may have a diameter of approximately 80 μm. Thetop-hat beam EL1 here provides a “basic intensity” on the area ofincidence AF. With the Gaussian beam EL2 moving over the circular path Karound the centre of the top-hat beam, the local intensity increase LIE(i.e. limited to a region along the circular path K) along the edge R ofthe overall intensity distribution GIV, which can be clearly seen inFIGS. 2 and 3, is achieved.

The second, smaller energy beam EL2 travels here at high speed (relativeto the scanning speed) along the circular path K, so that an area ofincidence AF on the build field 8 is exposed to the overall intensitydistribution GIV in a time-integrated manner (as mentioned over a periodof time with a certain duration, for example over a period), as shown inFIG. 2 and FIG. 3.

In order to ensure that the intensity on the intensity profile curve IPKin the scanning direction S has the maximum MAX at the front and theminimum MIN in the rear region and continuously decreases or increasesin between, the intensity of the second energy beam EL2 must bemodulated in a manner synchronised to the travel speed.

In principle, one or each of the functional regions F1, F2, F3 couldalso be plateau-shaped, so that the intensity distribution along theboundaries between the functional regions F1, F2, F3 is graded, forexample. However, a forming of functional regions by means of curvedintensity profiles or a design of the combined intensity distribution asa superimposition of different intensity profiles, as shown in FIGS. 2and 3, is usually technically easier and more cost-effective toimplement.

With the aid of FIGS. 4 to 6, examples will now be explained with whichsuch a combination energy beam AL can be generated in a particularlysimple and cost-effective manner.

In the first embodiment example according to FIG. 4, the irradiationdevice 20 has an energy beam source system 21 with two individual lasers21 a, 21 b. The first laser 21 a generates a laser beam EL1 as the firstenergy beam EL1 and is designed or provided with a beam shaping devicesuch that the first laser beam EL1 has the desired top-hat intensitydistribution. The second laser 21 b is designed to generate a laser beamEL2 with a Gaussian intensity distribution as a second energy beam EL2.In the following, the terms “laser beam” and “energy beam” are thereforeused synonymously—without limitation of generality.

This second laser beam EL2 is first radiated through a first energy beammovement unit 30, which provides for the movement of the second laserbeam EL2 relative to the first laser beam EL1. The first energy beammovement unit 30 here comprises a hollow shaft 31 which rotates at arotational speed Ω about a rotational axis RAh which corresponds to thelongitudinal axis of the hollow shaft 31. To drive the hollow shaft 31,it is equipped with a corresponding motor (not shown).

The beam path S2 or the beam axis S2 of the second laser beam EL2 runsin such a way that the laser beam EL2 is irradiated directly on therotation axis RAh into the hollow shaft 31. An optical element 32, moreprecisely a transmissive beam shift element 32, is arranged in thehollow shaft 31 or at its end and laterally shifts the Gaussian-shapedlaser beam 21B by a distance or an axial distance d from the rotationaxis RA. In the embodiment example shown, the transmissive beam shiftelement 32 is a flat plate 32. Due to the rotation of this flat plate 32on the hollow shaft 31, the Gaussian-shaped second laser beam EL2 or itsbeam axis S2 always moves parallel to the rotation axis RAh, but on acircular path which runs at an axial distance d around the rotation axisRAh. Integrated over one revolution over the circular path, a (virtual)“averaged beam axis” or an “averaged beam path” of the second laser beamEL2 would lie exactly on the rotation axis RAh, as already definedabove.

This rotating second energy beam EL2 is then combined with the firstenergy beam EL1 in a beam combiner 22, in this case a polariser 22 (forexample a thin-film polariser 22) of the energy beam combination device22, with care being taken to ensure that the virtual rotation axis RAvabout which the second energy beam EL2 rotates, i.e. the “averaged beamaxis” of the second laser beam EL2, runs behind the beam combiner 22coaxially to the beam axis S1 of the first energy beam EL1.

The axial distance d by which the beam axis S2 of the second energy beamEL2 is shifted relative to the rotation axis RA ultimately determinesthe radius of the intensity profile curve IPK in the overall intensitydistribution GIV of the combination energy beam AL (see FIG. 2) aroundthe beam axis SA, i.e. the radius of the circular path K. The axialdistance d is in this case the distance between the virtual rotationaxis RAv of the second energy beam EL2 and the centre of the secondintensity distribution SP2, so that here a diameter of the overallintensity distribution GIV is slightly greater than twice the axialdistance d.

Since the beam path S1 of the first laser beam EL1 and the “averagedbeam path” of the second energy beam EL2 run coaxially here, both laserbeams EL1, EL2 are thus coupled into the scanner 23, for example ontothe first scanner mirror of the scanner, on a common beam path.Therefore, the laser beams EL1, EL2 are coordinated and superimposed oneach other as a combination energy beam AL at the area of incidence AFon the build field 8 and are moved over the material 13 with thescanning speed and scanning direction specified by the scanner 23. Thescanning movement does not in itself influence the relative movement ofthe second energy beam EL2 within the combination energy beam AL.However, it can be advantageous to modify the movement, for example themovement speed, of the second laser beam EL2 relative to the first laserbeam EL1 or an intensity modulation of the second laser beam EL2depending on the scanning movement, i.e. the scanning direction and/orscanning speed.

FIG. 5 shows a further embodiment example of the irradiation device 20,with which a corresponding combination energy beam or combination laserbeam AL can be generated as an alternative to the embodiment in FIG. 4.Also in this embodiment example, the irradiation device 20 has an energybeam source system 21 with two separate lasers 21 a, 21 b for the firstenergy beam or laser beam EL1 and the second energy beam or laser beamEL2. Here, too, the first laser beam EL1 is generated with a top-hatintensity distribution and forwarded directly to a beam combiner 22.

However, the first energy beam movement unit 33 is constructeddifferently here than in the embodiment example according to FIG. 4.Here, the energy beam movement unit 33 comprises a first mirror 34, afurther mirror 35 that rotates during operation, and a converging lens37 as an optical element.

The—again Gaussian—second laser beam EL2 is first emitted onto the firstmirror 34 and from there is directed onto the rotating mirror 35, whichis oblique to the (incoming) beam path S2 of the irradiated second laserbeam EL2, the rotation axis RAs of the mirror 35 being coaxial to thebeam path S2 of the incoming laser beam EL2. This rotating mirror 35 isdriven by an electric motor 36, which can be controlled in a suitablemanner by the control device 50. Since a rotational movement of themirror 35 as a result of an inclined position of a mirror plane SE leadsto a corresponding movement of the mirror surface or mirror plane SE,the beam path S2 of the second laser beam EL2 is deflected in such a waythat, starting from the mirror 35, it initially moves over a conicalenvelope, so that the radius of the circular path increases withincreasing distance from the rotating mirror 35. In other words, thebeam path S2 of the second laser beam EL2 starting from the rotatingmirror 35 is tilted at an angle to the rotation axis RAs of the mirror35.

As shown in FIG. 5, a converging lens 37 is connected downstream of therotating mirror 35 in the further beam path as an optical element. Saidconverging lens is located, along the rotation axis RAs in the beampropagation direction starting from the rotating mirror 35, after thefirst mirror 34. The angle at which the beam path starting from themirror 35 runs, as well as the distances between the components 34, 35,37 and their dimensions, are selected so that the beam path S2 runs pastthis first mirror 34 in every position of rotation and impinges on theconverging lens 37.

The converging lens 37 is oriented here so that its optical axis iscoaxial with the rotation axis RA of the rotating mirror 35. Preferably,the converging lens 37 is designed in such a way that the output beamsof a laser beam that passes through it in a certain direction runparallel to the rotation axis RA. It thus deflects the incoming secondlaser beam EL2 moving on a path in the form of a conical envelope ororients it in such a way that the beam path S2 of the second laser beamEL2 runs parallel in the further course after the converging lens 37,namely radially offset at a fixed axial distance d from the (imaginaryextended) rotation axis RAs (i.e. a virtual rotation axis RAv).

In this construction, the axial distance d—and thus the radius d of therotating circular path of the second laser beam EL2 around the rotationaxis RA—can be adjusted by changing the distance between the converginglens 37 and the rotating mirror 35 and/or the inclination of therotating mirror 35. In the event of a change in distance duringoperation of the irradiation device 20, the converging lens 37 must besupplemented by an optical unit for adjusting its focus. This is thefocal point of the converging lens 37 which lies on the side of theconverging lens 37 facing the rotatable mirror 35 (i.e. on the inputside). This focal point of the converging lens 37 is (within usualtolerances) preferably always in the mirror plane of the rotating mirror35, moreover in its centre of rotation, during the use of theirradiation device 20 for the solidification of build-up material.

In this embodiment example, too, over a revolution over the circularpath, a (virtual) “averaged beam axis” or an “averaged beam path” of thesecond laser beam EL2 would therefore lie exactly on the rotation axisRAs of the mirror, since this corresponds to the virtual rotation axisRAv about which the second laser beam EL2 rotates. The virtual rotationaxis RAv and thus the “averaged beam axis” of the second laser beam EL2as well as the beam path S1 of the first energy beam EL1 are againaligned here in such a way that they impinge on a beam combiner 22 ofthe energy beam combining device 22, such that the periodically averagedvirtual beam path of the second energy beam EL2 according to the abovedefinition is coaxial with the beam path S1 of the first energy beam EL1and thus the beam path S2 of the second energy beam EL2 rotates inparallel around the beam path S1 of the first energy beam EL1 with theaxial distance d in each case. As in the embodiment example according toFIG. 4, the combination energy beam AL generated in this way can then becoupled into the scanner 23.

A further modification is shown in FIGS. 6 and 6 a, with FIG. 6a showingthe first energy beam movement unit 33′ from FIG. 6 on an enlarged scaleto explain the angular positions in greater detail. The constructionused here is very similar to the construction in FIG. 5. However, thefirst energy beam movement unit 33′ is constructed here in such a waythat the first mirror 34 can be dispensed with. Instead, the rotationaxis RAr of the rotating mirror 35′ (and the electric motor 36′) is nownot arranged coaxially to the optical axis of the converging lens 37′ asin the embodiment example according to FIG. 5, but is at an angle of 45°to it.

A mirror plane SE of the rotating mirror 35′ is additionally tilted atan angle α to a perpendicular to the rotation axis RAs of the mirror35′. In other words, a periodically averaged (virtual) mirror planeaccording to the definition given above is twisted around the centre ofrotation RZ of the mirror 35′ as a pivot point at an angle α. Thisrotation or inclined position can be fixed by fixing the mirror 35′ atits rotation axis RAs. Alternatively, it can be variable if the mirror35 and its rotation axis RAs are mechanically connected to each other,for example by a joint, with said joint being adjustable by an electricmotor.

If, as shown, the second laser beam EL2 is then irradiated by the secondlaser 21 b at 90° to the optical axis of the converging lens 37, i.e.also at 45° to the rotation axis RA of the rotating mirror 35, onto thecentre of rotation RZ of the rotating mirror 35′, it is forwarded fromthere, tilted at a corresponding angle 2·α to the optical axis of theconverging lens 37′, onto the converging lens 37. Since a rotationalmovement of the mirror 35′ as a result of an inclined position of themirror plane SE by the angle α leads to a corresponding movement of themirror surface or mirror plane SE, the second laser beam EL2 thusinitially moves here from the mirror 35′ over a conical envelope and isdeflected or oriented again by the converging lens 37′ in such a waythat the beam path S2 of the second laser beam EL2 runs parallel to theoptical axis of the converging lens 37′ in the further course after theconverging lens 37′. For this purpose, the focal point or focus of theconverging lens 37′ on the input side must lie on the mirror plane SEand in the centre of rotation RZ of the mirror 35′.

In this embodiment, the axial distance d—and thus the radius d of thecircular path around the optical axis of the converging lens 37 (i.e.the “virtual rotation axis” RAv about which the second laser beam EL2rotates) created as a result of the rotational movement of the secondlaser beam EL2—can be adjusted by changing the inclined position of therotating mirror 35′ (i.e. by an angle α±x). The requirements describedabove for the beam path of the second laser beam EL2 are fulfilled ifthe converging lens 37′ is designed or its focal length f is selected insuch a way that its focal point on the input side lies on the mirrorplane SE and in its centre of rotation RZ, even with a greater or lesserdeflection of the second energy beam reflected by the mirror 35′, andits focal point on the output side lies at infinity, so that thepotential beam paths of an outgoing second laser beam EL2 run parallelto one another.

All other components can be designed and arranged identically in theembodiment examples according to FIGS. 5 and 6 (with 6 a).

The irradiation devices 20 shown in all three FIGS. 4 to 6 each comprisehere a monitoring device 26. For this purpose, a beam splitter 27 isintroduced in the beam path in each case and branches off a small partof the intensity of the combination energy beam AL into a monitoringsystem 28 for measuring and checking the overall intensity distributionGIV of the combination energy beam AL. The monitoring system 28 maycomprise an area sensor that records an integral image/signal of theoverall intensity distribution GIV. In this way, for example in themonitoring system 28 or in the control device 50, an actual rotation ofthe overall intensity distribution GIV can be compared with a targetrotation and/or an actual distribution can be compared with a targetdistribution of the intensity distribution and, if necessary, therelevant actual setting can be readjusted by means of an additionalcontrol loop (not shown).

In all embodiment examples previously explained in detail, therotational speed Ω is selected such that the magnitude of the speed atwhich the second energy beam EL2 travels on the circular path K in theoverall intensity distribution GIV of the combination energy beam AL ishigh in relation to the corresponding scanning speed S.

In order to achieve the intensity maximum value MAX and the intensityminimum value MIN on the intensity profile curve IPK along the circularpath K at the edge R of the top-hat intensity distribution, theintensity of the second energy beam EL2 can be modulated in each caseduring its movement over the course of the circular path. For thispurpose—in particular also in the two constructions according to FIGS. 4to 6—the power L of the second laser 21 b can be modulated in thesimplest case with a generator signal GS, as shown in FIG. 7.

For simplification, the modulation is described here as a function ofthe polar angle 9 on the circular path, and in FIG. 7 the amplitude A ofthe generator signal GS, which is correlated with the power to beemitted by the second laser 21 b and consequently the absolute intensityof the second laser beam, is plotted in arbitrary units [a. u.] over theangle 9 (which in FIG. 6 runs from −π to +π). At angle φ=0, the maximumamplitude of the generator signal GS is present and drops to a minimumvalue at angle φ=+/−π, so that the absolute intensity of the second,Gaussian-shaped laser beam EL2 periodically oscillates sinusoidallybetween a minimum value and a maximum value during one revolution overthe circular path K. Without limiting generality, it is assumed herethat the angle φ=0 is at the front in the scanning direction S.Accordingly, the intensity maximum value MAX of the total intensitydistribution GIV is located at the front in the scanning direction S,and an intensity minimum value MIN is located at the rear, as shown inFIGS. 2 and 3.

By a simple phase shift of this generator signal GS, the maximum valueMAX and the minimum value MIN can be shifted on the circular path K,i.e. rotated about the centre of rotation or the beam axis S1 of thetop-hat intensity distribution. This is important in the event that thescanning direction over the build field 8 is changed, but possibly alsofor an adaptation of the overall intensity distribution GIV or theposition of the maximum value MAX to an environment parameter at thecurrent area of incidence AF.

The relative intensity differences between the maximum value MAX and theminimum value MIN on the intensity profile curve IPK can be adjusted bythe amplitude A of the generator signal GS for the second laser beam EL2shown in FIG. 7, for example. This is shown by way of example in FIG. 8on the basis of three overall intensity distributions GIV shown side byside, with all overall intensity distributions GIV having the same basicshape and differing only in the heights of the maximum and the minimumor in the shape of the intensity profile on the intensity profile curveIPK along the circular path K along the edge of the overall intensitydistribution GIV. Therefore, the basic shape of the overall intensitydistribution GIV is distorted, with the minimum MIZ is being shiftedbackwards here in a direction opposite the scanning direction or withrespect to the scanning direction within the overall intensitydistribution GIV.

The exact form of the overall intensity distribution GIV that is optimalfor the current manufacturing process can depend on various otherprocess parameters, including the current scanning speed, amongstothers.

FIG. 8 shows on the left side, for example, a simulation for an overallintensity distribution GIV at a scanning speed of 0.1 m/s. In themiddle, an overall intensity distribution GIV for a scanning speed of1.6 m/s is shown. The right-hand side shows an overall intensitydistribution GIV for a scanning speed of 3.1 m/s. All overall intensitydistributions GIV comply with the above criteria according to theinvention.

By comparing the three overall intensity distributions GIV it can beseen that with increasing scanning speed the maximum value MAX increasesin relation to the minimum value MIN on the intensity profile curve IPK.In other words, the functional region F2 “heat” (see FIG. 2 with theexplanations in this regard) is particularly significantly increased inrelation to the functional region “hold” F1. This can be simplyexplained by the fact that the functional region F1 “hold” is onlyneeded as a “heat loss compensation area” to compensate for the lossesdue to heat flows within temperature differences between the weld pooland the surrounding material. An extent of the functional region F1“hold” can thus scale with the material values, in particular thethermal conductivity, the thermocapillary convection and the temperaturedistribution in the vicinity of the weld pool. Especially withincreasing speed, however, it loses significance compared to the otherdefined functional regions.

The functional region F2 “heat”, on the other hand, is needed to preheator heat up as yet unsolidified cold build-up material 13 or, to someextent, already solidified material of a neighbouring track (for examplea neighbouring hatch) to the melting temperature. This region inparticular scales with the speed of the area of incidence. Withincreasing scanning speed, the heating must take place correspondinglyfaster, i.e. more intensity is required and the maximum becomes higherand accordingly the functional region F2 also becomes wider, i.e. thefunctional region F2 extends far beyond the centre of the overallintensity distribution GIV to the rear. In the extreme case (seeright-hand overall intensity distribution GIV in FIG. 8), the minimumvalue MIN of the profile curve IPK also corresponds to the absoluteminimum MIZ of the overall intensity distribution GIV. Nevertheless, ascan be seen in FIG. 8, the overall intensity distribution GIV still hasa local minimum in the middle region with respect to a secant SK, sincethe second laser beam EL2 on the intensity profile curve IPK providesfor a local increase of the overall intensity distribution GIV. Thesecant SK runs here perpendicularly to the scanning direction S throughthe centre of gravity (of the geometric figure) of the overall intensitydistribution GIV, which is shifted slightly forward here in the scanningdirection S between the centre through which the rotation axis or beamaxis SA of the overall intensity profile GIV runs and the maximum valueMAX.

It should be mentioned here that, quite generally, the functionalregions can also take up an area-variable share of the overall intensityprofile depending on certain constraint, such as the “scanning speed”and/or the “available maximum intensity” or “available power”, byappropriately (in particular also dynamically) prescribing the controlparameters for the energy beam, in particular for the combination energybeam.

FIG. 9, in this regard, shows a greyscale image SB of the intensitydistribution of the combination energy beam, as would result, forexample, from a beam as shown in FIG. 8 on the right. The light areashere are the areas with particularly high energy beam intensity. Theseclearly show a crescent shape or the shape of a half moon with the bellyin the direction of the scanning direction S. This means that at the“leading edge” of the overall intensity distribution GIV, which firsthits the material during the course of the feed movement or scanningmovement, there is a strong intensity increase measured against theaverage intensity, which then drops off relatively steeply in the rearregions to then taper off gently and flatly towards the rear edge.

As mentioned above, in the embodiment examples shown, for example, asimple phase shift of the generator signal GS shown, for example, inFIG. 7, allows the second laser 21 b to be controlled in such a way thatthe maximum value MAX and the minimum value MIN on the intensity profilecurve IPK are shifted, i.e. such that the overall intensity distributionGIV is rotated about the centre of rotation or the beam axis SA of theoverall intensity distribution GIV.

As mentioned, this may be necessary in case of a change of direction ofthe scanning movement, for example in case of a hatch reversal, if, whenfollowing the hatching course, the neighbouring hatch is to be scannedin the opposite direction at the end of a hatching line (hatch) in aradiation strip. On the other hand, however, it is also advantageous ifthe exact design of the overall intensity distribution GIV can beadapted to the area of incidence environment parameters, in particularto whether the current solidification takes place on a track or a hatchthat runs parallel to an already solidified area.

For this purpose, reference is made to FIG. 10 by way of example. In theupper image, four hatch tracks HE are shown here by way of example, withthe area of incidence AF currently running in a scanning direction Salong a first track HE, next to which there is not yet a solidifiedneighbouring track. Accordingly, the overall intensity distribution GIVis preferably oriented such that the maximum in the scanning direction Sis exactly at the front and the minimum MIN is at the rear. In otherwords, the overall intensity distribution GIV is axially symmetricalwith respect to a symmetry axis AS running parallel to the scanningdirection S or coaxial to the scanning direction S.

The lower region of FIG. 10 shows the situation during solidification ina subsequent track HE, where the previous, immediately adjacent track isstill warm but already solidified. Here it is advantageous if theintensity profile curve IPK is slightly rotated with respect to thescanning direction S, so that the maximum value MAX is somewhat furtheraway from the already solidified region VB of the first track HE and theminimum MIN is somewhat closer to the solidified region VB. In otherwords, here the overall intensity distribution GIV is deliberately notaxially symmetrical with respect to the axis of symmetry AS definedabove, which is coaxial with the scanning direction S. The reason forthis is that energy has already been introduced into the neighbouringhatch during its solidification. This is because the solidification ofthe individual adjacent hatches usually takes place in short timeintervals, within which, typically, the melted build-up material doesnot cool completely, for example to an ambient temperature in theprocess chamber or in the build volume. Therefore, only the energy thatis not dissipated by heat conduction into the material below needs to beprovided to bind a current track HE to the immediately previouslysolidified, adjacent track HE. Here the scanning paths are shownstrictly separated, or rather the overall intensity distribution is notlarger than a single scanning path. In principle, however, an overlapwould also be conceivable.

If the neighbouring track HE has already cooled down because it wassolidified a relatively long time before the current track HE, it can beuseful to orient the maximum value MAX of the overall intensitydistribution for the irradiation of the current track HE in thedirection of the already solidified and cooled track or to turn it froman initial position according to the upper illustration of FIG. 10. Inthis case, heat conduction is increased in the region of the currenttrack HE to be solidified near the solidified track HE, so that moreenergy must be introduced there to achieve the desired solidification.This variant, however, is not shown in any of the figures.

It is also possible to change strategy during the solidification of asingle track, as shown schematically in FIG. 11.

If, for example, a current track HE is solidified in the oppositedirection to a relatively long, previously solidified, immediatelyadjacent track HE, then at the beginning of the current track HE apreviously solidified, adjacent region VB is relatively hot, since onlyrelatively little time has passed since it was solidified. Towards theend of the track HE, however, the neighbouring solidified region VBbecomes increasingly colder. Accordingly, the maximum value MAX at thebeginning (position P₁) of the current track HE can be turned away fromthe neighbouring solidified region VB, i.e. it can be arranged closer toa track HE which is directly adjacent to the current track and whichpossibly is to be solidified subsequently, than to the solidified regionVB. In the further course of the irradiation in the scanning directionS, the maximum value MAX of the overall intensity distribution is thenrotated in such a way that it lies on the axis of symmetry AS (positionP₂) and then successively, preferably continuously, is further rotatedin such a way that at the end of the current track HE it is rotatedtowards the adjacent solidified region VB (position P₃), i.e. it liescloser to the solidified region VB than to a track HE which liesdirectly adjacent to the current track and which possibly is to besolidified subsequently.

FIGS. 12a to 12e show further possible (overall) intensity distributionsthat can also be generated by the (“smaller”) second energy beamtravelling along cyclic paths; here, in all cases, the path of thesecond energy beam again runs approximately parallel inside an edge ofthe energy distribution of the (“larger”) first energy beam. In allcases, the first energy beam again has a plateau (“flat-top” or “top-hatintensity distribution”), but has a different geometric base area. Inother words, the intensity distribution is spatially relativelyhomogeneous across the beam cross section with a relatively sharp edge.Such first energy beams with such energy distributions can also begenerated with suitable beam-shaping units, such as diffractive opticalelements (DOEs).

Specifically, FIG. 12a shows an intensity distribution with a hexagonalor honeycomb-shaped base area, with a corner lying at the front in thescanning direction S. FIG. 12b shows an intensity distribution with aquadrangular base area, and here as well a corner lies at the front inthe scanning direction S. By contrast, in FIG. 12c the quadrangular basearea of the intensity distribution is oriented such that an edge of thequadrangle (here a square) lies at the front in the scanning directionS. FIGS. 12d and 12e here show two triangular variants, once with afront edge perpendicular to the scanning direction S (FIG. 12d ) andonce with a tip or corner at the front in the scanning direction S (FIG.12e ).

As can be seen, however, all intensity distributions GIV shown in FIGS.12a to 12e fulfil the criteria according to the invention in that theyhave at least one local minimum in a middle region along at least onesecant of the intensity distribution in the section plane and in thatthey have an intensity profile curve running along an edge of theintensity distribution, which intensity profile curve has a maximumvalue at least at one point and a minimum value at least at one point ina region opposite the maximum value on this intensity profile curve.

In all cases, the second energy beam is also modified here in itsintensity over the course of its path in such a way that, in each case,an intensity maximum or a maximum range (in the case of thedistributions with the edges lying at the front) of the intensitydistributions lies at the front in scanning direction S.

In practice, the edges or corners of the geometric figures of theintensity distributions shown in the figures with sharp edges can alsobe produced with rounded edges (for example due to the inertia of movingcomponents of the beam generation or beam deflection).

Lastly, it is pointed out once again that the devices described indetail above are merely embodiment examples which can be modified by aperson skilled in the art in a wide range of ways without departing fromthe scope of the invention. In particular, it is noted once again that acombination energy beam with a suitable overall intensity distributioncan also be generated by ensuring, with two appropriately coordinated orsynchronised controlled scanners at any time, that the first and thesecond energy beam are in the appropriate position superimposed on eachother in the area of incidence, wherein the scanner for the secondenergy beam can then be moved correspondingly faster than the scannerfor the first energy beam. It would also be possible, for example, tomove an irradiation device with at least two beam sources together inorder to move the area of incidence of the combination energy beam,whereby one of the beam sources additionally or superimposed executes a(preferably fast) relative movement to the other beam source, or atleast the energy beam of one of the beam sources moved together can bemoved relative to the energy beam of the other beam source with amovement unit provided for this purpose, for example with a mirror etc.Furthermore, in addition to the relative movement of the two energybeams with respect to each other, it would also be possible to use a(different) focus change or focus widening/defocusing of the energybeams. Likewise, the “shaping” of the energy beam, i.e. the generationof an intensity distribution according to the invention, could also beachieved by completely different means, as already mentioned. Lastly, itis again noted that the method could also be used for other processesbesides additive manufacturing, for example for a welding of seams orthe like. Furthermore, the use of the indefinite article “a” or “an”does not exclude the possibility that the features in question may bepresent more than once. Similarly, the term “unit” does not exclude thepossibility that it consists of a number of interacting sub-components,which may also be spatially distributed.

REFERENCE LIST

-   1 additive manufacturing device/laser sintering device-   2 manufacturing product/object/component-   3 process area/process chamber-   4 chamber wall-   5 container-   6 container wall-   7 working plane-   8 build field-   10 support-   11 base plate-   12 build platform-   13 build-up material-   14 storage container-   16 coater-   17 radiation heater-   18 sensor arrangement/camera-   20 irradiation device/exposure device-   21 energy beam source system/laser system-   21 a laser-   21 b laser-   22 energy beam combination device/beam combiner-   23 second energy beam movement unit/scanner/deflection unit-   24 focusing device-   25 coupling window-   26 monitoring device-   27 beam splitter-   28 monitoring system-   30 first energy beam movement unit-   31 hollow shaft-   32 optical element/transmissive beam shift element/flat plate-   33 first energy beam movement unit-   33′ first energy beam movement unit-   34 first mirror-   35 rotating mirror-   35′ rotating mirror-   36 rotation unit/electric motor-   36′ rotation unit/electric motor-   37 converging lens-   37′ converging lens-   50 control device-   51 control unit-   52 quality data determination device-   53 irradiation control interface-   54 control data generation device-   54′ control data generation device-   55 bus-   56 terminal-   A amplitude of the generator signal-   AF area of incidence-   AL (output) combination energy beam/laser beam-   AS symmetry axis-   B section plane-   d axial distance-   DS beam extent/diameter-   EL1 first energy beam/laser beam-   EL2 second energy beam/laser beam-   f focal length-   FS focus control data-   F1 functional region “hold”-   F2 functional region “heat”-   F3 functional region “shape”-   GS generator signal-   H horizontal direction-   HE hatch tracks-   HS heating control data-   GIV overall intensity distribution-   IPK intensity profile curve-   K circular path-   LIE local intensity increase-   LSa, LSb laser control data-   MAX local maximum value-   MIN local minimum value-   MIZ minimum-   PST process control data-   P₁, P₂, P₃ positions-   QD quality data-   R edge-   RAh hollow shaft rotation axis-   RAs mirror rotation axis-   RAv virtual rotation axis-   RS relative movement control data-   RZ rotation centre-   S direction of movement of the area of incidence/scanning direction-   SA beam path/beam axis of the combination energy beam-   SB greyscale image-   SD scan control data-   SE mirror plane-   SK secant-   SP1 first intensity distribution/top-hat intensity distribution-   SP2 second intensity distribution/Gaussian intensity distribution-   ST coating control data-   S1 beam path/beam axis of the first energy beam-   S2 beam path/beam axis of the second energy beam-   TS support control data-   V vertical direction-   VB solidified region-   x, y plane-   z direction-   Ω rotation speed-   α angle-   φ polar angle

1. A method for generating control data for a device for the additive manufacture of a manufacturing product in a manufacturing process in which build-up material is built up and selectively solidified, wherein, for the solidification process, the build-up material is irradiated with at least one energy beam on a build field, wherein an area of incidence of the energy beam on the build field is moved in order to melt the build-up material, and wherein the control data are generated such that the energy beam has an intensity distribution, at the area of incidence on the build field, in a section plane running perpendicularly to the beam axis of the energy beam, which intensity distribution has at least one local minimum in a middle region along at least one secant of the intensity distribution in the section plane and has an intensity profile curve, running along the edge of the intensity distribution, which intensity profile curve has, at least at one point, a maximum value, and, at least at one point in a region opposite the maximum value on the intensity profile curve, a minimum value.
 2. The method according to claim 1, wherein the intensity distribution has a local intensity increase which extends in an at least partially annular circumferential edge region of the intensity distribution.
 3. The method according to claim 1, wherein the maximum value on the circumferential intensity profile curve lies in an edge region of the intensity distribution lying at the front in a scanning direction of the energy beam on the build field.
 4. The method according to claim 1, wherein the minimum value on the intensity profile curve is higher than the local minimum in the middle region of the intensity distribution, wherein the intensity on the intensity profile curve is preferably higher than the local minimum in the middle region of the intensity distribution at any point.
 5. The method according to claim 1, wherein the ratio of the maximum value on the circumferential intensity profile curve to the intensity in a local minimum is at most 10:1, and/or wherein the ratio of the minimum value on the circumferential intensity profile curve to the intensity in the local minimum is at least 1.5:1.
 6. The method according to claim 1, wherein the maximum value on the intensity profile curve is at least one and a half times in the region opposite on the intensity profile curve and/or wherein the maximum value on the intensity profile curve is a maximum of eight times higher than the minimum value in the region opposite on the intensity profile curve.
 7. The method according to claim 1, wherein the intensity profile curve is curved between the maximum value and the minimum value in the region opposite on the intensity profile curve.
 8. The method according to claim 1, wherein the intensity distribution of the energy beam is set to be substantially axially symmetrical or substantially non-axially symmetrical depending on an area of incidence environment parameter, with respect to an axis of symmetry lying in a scanning direction.
 9. The method according to claim 1, wherein control data for generating at least two energy beams are generated, so that the intensity distribution is generated by a superimposition of the energy beams, wherein preferably the control data are generated in such a way that a first energy beam together with a second energy beam at least partially superimposed as a combination energy beam is moved in a coordinated manner over the build field at a predetermined scanning speed and at the same time a, preferably cyclic, relative movement of the second energy beam with respect to the first energy beam takes place at a predetermined relative speed, the magnitude of which is much greater than the scanning speed, wherein the second energy beam is intensity modulated depending on its relative position to the first energy beam and/or depending on a current direction of movement of the area of incidence of the combination energy beam.
 10. The method according to claim 1, wherein the control data are generated with determination of further process parameters in such a way that, when the device is controlled using the control data, the build-up material within a target region is melted by means of heat conduction welding.
 11. A method for controlling a device for the additive manufacture of a manufacturing product, wherein control data for the device are generated according to a method according to claim 1 and the device is controlled using said control data.
 12. A control data generation device for generating control data for a device for the additive manufacture of a manufacturing product in a manufacturing process in which build-up material is built up and selectively solidified, wherein, for the solidification process, the build-up material is irradiated with at least one energy beam on a build field, wherein an area of incidence of the energy beam on the build field is moved in order to melt the build-up material, wherein the control data generation device is designed in such a way that the control data are generated such that the energy beam has an intensity distribution, at the area of incidence on the build field, in a section plane running perpendicularly to the beam axis of the energy beam, which intensity distribution has at least one local minimum in a middle region along at least one secant of the intensity distribution in the section plane and has an intensity profile curve, running along the edge of the intensity distribution, which intensity profile curve has, at least at one point, a maximum value, and, at least at one point in a region opposite the maximum value on the intensity profile curve, a minimum value.
 13. A control device for a device for the additive manufacture of a manufacturing product in a manufacturing process, in which build-up material is built up and selectively solidified, wherein, for the solidification process, the build-up material is irradiated with at least one energy beam on a build field, wherein an area of incidence of the energy beam on the build field is moved in order to melt the build-up material, wherein the control device has a control data generation device according to claim 12 or an interface to a control data generation device for providing control data and is configured to control the device for irradiating the build-up material with the energy beam using this control data.
 14. A device for the additive manufacture of manufacturing products in an additive manufacturing process, having at least one feed device for introducing build-up material into a process area, having an irradiation device for selectively solidifying the build-up material by irradiation by means of at least one energy beam, and having a control device according to claim
 13. 15. A computer program product having a computer program which can be loaded directly into a control device of a device for the additive manufacture of manufacturing products, having program sections to execute all steps of the method according to claim 1 when the computer program is executed in the control device.
 16. Control data for controlling an additive manufacturing device, which control data are configured to control the additive manufacturing device in such a way that a manufacturing product is manufactured using a method according to claim
 11. 